WO2015019347A1

WO2015019347A1 - Girk as a therapeutic target of immune disorders and a marker of b cell subtypes

Info

Publication number: WO2015019347A1
Application number: PCT/IL2014/050701
Authority: WO
Inventors: Eitan Reuveny; Erez S. GARTY; Avraham Ben-Nun; Ayelet KAMINITZ
Original assignee: Yeda Research And Development Company Ltd.
Priority date: 2013-08-08
Filing date: 2014-08-04
Publication date: 2015-02-12

Abstract

The present invention is directed to methods for treating immune disorders, inter alia, multiple sclerosis, comprising administering a therapeutically effective amount of at least one G protein gated Inward Rectifying K+ channel (GIRK) inhibitor to a subject in need thereof. The present invention further provides GIRKs as markers of B cell subtypes.

Description

GIRK AS A THERAPEUTIC TARGET OF IMMUNE DISORDERS AND A MARKER

OF B CELL SUBTYPES

FIELD OF THE INVENTION

BACKGROUND OF THE INVENTION

Ion channels Ion channels are membrane-embedded proteins involved in neuronal transduction, muscle contraction, hormone secretion, apoptosis, immune response and many other processes. They mediate cellular functions by controlling the membrane potential in excitable cells and the cellular ionic homeostasis. They do so by using the electrochemical gradient between the intra and extracellular matrixes. In addition to their diverse physiological functions, their mode of gating is also diverse and involves changes in transmembrane voltage, ligand binding, signal transduction pathways, and physical stimuli. Many ion channels can be regulated by a combination of several mechanisms.

GIRK channels

The G protein-coupled inwardly-rectifying potassium channels (GIRKs) is a family of inward-rectifier potassium ion channels which are activated via the ligand-stimulated G protein-coupled receptors (GPCRs) signal transduction cascade. This ion channel family consists of four members, GIRK1-4, in mammals with various expression patterns in various tissues. Upon their activation, potassium ion movement across the membrane causes membrane potential decrease (hyperpolarization) that reduces cellular excitability. The GIRKs are also known as Kir3.x, where x refers to an unspecified subtype of the Kir3 family.

One member of this family, GIRK4, was cloned in 1995 and was found to form heterotetramers with GIRK1 at a 2:2 ratio. Together they create the inward-rectifying potassium channel "Muscarine potassium current (ΙΚΑΛ)" which is responsible for heart rate decrease upon acetyl choline secretion from the vagus nerve. GIRK4 is also capable of forming functional homo-tetramers and is found in organs such as the pancreas, kidney, lung, spleen and the brain. Previous studies have shown that GIRK knockout mice (GIRK4^_/~ mice) exhibit abnormal heart rate (Wickman, K., (1998) Neuron 20(1): 103-14), slight problems in memory and learning (Wickman, K., et al. (2000) J. Neurosci. 20(15):5608-15), and a tendency for late onset obesity (Perry, C. A., et al. (2008) Proc. Natl. Acad. Sci USA 105(23):8148-53). GIRK4 was also shown to be expressed in platelets, where it was shown to be involved in P2Y12 dependant aggregation (Shankar, H., et al., (2004) Blood 104(5): 1335- 43). Although numerous data has been accumulated for GIRKs, their role in the immune system is still unknown.

International Patent Application Publication No. WO 2005/054863 discloses nucleic acid sequences and amino acid sequences of a human GIRK3 and its regulation for the treatment of various diseases, inter alia, cardiovascular disease.

International Patent Application Publication No. WO 2003/094903 discloses a composition useful in reducing neuronal cell death, comprising an ion channel blocker such as a K+ channel blocker and one or more pharmaceutically acceptable carriers.

International Patent Application Publication No. WO 2011/068801 discloses inward rectifier K+ (Kir) channel proteins and methods for identifying compounds that modulate ion channel activity by Kir channels. B lymphocytes

B lymphocytes are antibody-secreting lymphocytes that play an important role in the adaptive immune system. B cell maturation and differentiation follows distinct developmental stages that initiates in the bone marrow, where B cell precursors develop into pro- and pre-B cells while rearranging their immunoglobulin light and heavy chain genes. B cell maturation and differentiation is proceeding further in secondary lymphoid organs. B cells have been divided into different populations according to their differentiation stage in the lymphoid organs. The classical B lymphocytes, termed B-2 lymphocytes, are capable of binding antigens, present fragments thereof on Major Histocompatibility Complex Class II (MHC II) receptor and either differentiate to become an antibody secreting cell (a plasma cell) or become a memory B cell. Another group of B cells, termed B-l cells, are a separate lineage of B lymphocytes located mostly in body cavities such as the pleural and peritoneal. B-l lymphocytes are known to secrete "natural antibodies" capable of recognizing antigens presented by various pathogens, such as Lipopolysaccharide (LPS) and Phosphatidylcholine (PC), and antigens of common pathogens such as Streptococcus pneumonia and the influenza virus. B-l cells are divided into two main subgroups, B-la and B-lb, which are distinct from each other and from B-2 lymphocytes by several membrane markers. B-la cells are the major producers of natural antibodies, while B-lb have an important role in defense against common pathogens.

In the past few years, growing data supports the existence of another type of B cells, termed regulatory B cells or B IO cells. These B lymphocytes reside mostly, but not only, in the peritoneal cavity. Regulatory B cells are considered as negative regulators of the immune response, and were shown to modulate several autoimmune and inflammatory diseases such as Multiple Sclerosis (MS), Inflammatory Bowel Disease (IBD) and type 1 Diabetes (Yang, M., et. al. (2013) Cell Mol. Immunol. 10(2): 122-32). Regulatory B cells share membrane markers overlapping with several B cell subtypes, making it very difficult to differentiate them from other B cell populations. One characteristic associated with those cells is IL-10 secretion. However, IL-10 secretion can only be detected following 5 hour of stimulation with agents that elicit an immune response. Although several attempts were made to classify and categorize regulatory B cells by membrane markers, organ origin or way of activation, to date there is no model that allows simple and reliable differentiation of those cells.

Multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) characterized by neurological impairment of variable extent, resulting from primary demyelination and axonal damage. This disease usually occurs in young adults, more commonly in women. Although the etiology of the disease is not yet known, evidence suggests that autoimmune mechanisms directed against myelin components in the CNS play an important pathogenic role. Regulatory B cells were shown previously to inhibit MS-like diseases progression by secretion of IL-10 (DiLillo, D. J., et al. (2010) Ann. N Y Acad. Sci., 1183:38-57). There remains an unmet medical need for novel and efficient therapies of immune disorders including, but not limited to, multiple sclerosis. It would also be advantageous to have a specific accessible marker for B regulatory cells as well as for B-la cells.

SUMMARY OF THE INVENTION The present invention is directed to compositions and methods for treating immune disorders, comprising administering to a subject in need thereof at least one G protein- coupled inwardly-rectifying potassium channel (GIRK) inhibitor. The invention further relates to GIRK as a marker of B cells, particularly of B-la cells and regulatory B cells.

The present invention is based, in part, on the unexpected discovery that GIRK4 is expressed on B cells and in particular is expressed in high levels on regulatory B cells and B- la cells. Regulatory B cells are known to be involved in the regulation of a wide variety of immune responses. To date, there is no membrane marker for identifying regulatory B cells. Hitherto, B regulatory cells could only be distinguished by detection of IL-10 secretion following at least 5 hours of stimulation with agents that elicit an immune response, such as lipopolysaccharides (LPS). Hence, the present invention provides, for the first time, a membrane marker for regulatory B cells. GIRK channels expression may be detected simply using, e.g., antibodies directed to GIRK, to thereby identify regulatory B cells. The methods of the invention are applicable for research as well as diagnostic applications.

The present invention is further based on the discovery that GIRK4 knockout mice (GIRK ^/_ mice) display delayed onset and reduced severity of clinical signs accompanying the Experimental Autoimmune Encephalomyelitis (EAE) mouse model as compared to wt mice. Further, GIRK4 was demonstrated to be associated with B and T cells migration and with reduced T cell stimulation and antigen presenting activity (APC).

Without being bound by any theory or mechanism of action, these findings indicate that GIRK possesses an important role in mediating immune disorders by modulating T cells activation and by affecting the role of B regulatory cells as negative regulators of the immune response. Thus, the present invention further provides GIRKs as targets for treating immune disorders, such as autoimmune and inflammatory diseases. According to one aspect, the present invention provides a method of treating an immune disorder in a subject in need thereof, comprising the step of administering to the subject a therapeutically effective amount of at least one G protein gated Inward Rectifying K+ channel 4 (GIRK4) inhibitor, thereby treating the immune disorder.

According to another aspect, the present invention provides a pharmaceutical composition comprising at least one GIRK4 inhibitor for use in treating an immune disorder.

According to yet another aspect, the present invention provides a method for identifying a B cell as a regulatory B cell or as a B- la cell, comprising the step of detecting the presence of a GIRK protein in the membrane of the B cell.

According to yet another aspect, the present invention provides a method for identifying a B cell as a regulatory B cell or as a B- la cell, comprising the step of detecting the presence of an RNA molecule encoding a GIRK protein in the B cell.

The present invention further provides, in another aspect, a kit for the treatment of an immune disorder, comprising a pharmaceutical composition comprising at least one GIRK4 inhibitor and a carrier; and instruction for use of the pharmaceutical composition for the treatment of the immune disorder.

The present invention further provides, in another aspect, a kit for identifying a B-cell as a regulatory B cell or as a B-la cell, the kit comprising an agent capable of identifying the presence of a GIRK protein in the membrane of the B cell; and instruction for use.

The present invention further provides, in yet another aspect, a kit for identifying a B- cell as a regulatory B cell or as a B-la cell, the kit comprising an agent capable of identifying the presence of a RNA molecule encoding a GIRK protein in the B cell; and instruction for use.

According to some embodiments, the GIRK4 inhibitor inhibits GIRK4 activity in lymphocytes. According to some embodiments, the GIRK4 inhibitor is capable of at least one activity selected from reducing the overall expression of GIRK4, neutralizing the functionality of GIRK4, inducing GIRK4 degradation, or any combination thereof. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the lymphocytes are selected from the group consisting of T cells and B cells. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the B cells are selected from the group consisting of B-la cells, regulatory B cells (BIO cells), B-lb cells and B-2 cells. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the B cells are B-la cells.

According to some embodiments, the GIRK4 inhibitor is an antibody or an antigen- binding fragment thereof, capable of binding to GIRK4. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the GIRK4 inhibitor is selected from the group consisting of Tertiapin (TPN), Charybdotoxin, Bupivacaine, Ethosuximide, SCH23390 (R(+)- 7-chloro-8-hydroxy-3-methyl-l-phenyl-2,3,4,5-tetrahydro-lH-3-benzazepine hydrochloride) and U50488H (trans-(+/-)-3 ,4-dichloro-N-methyl-N- [2-(pyrrolidinyl)cyclohexyl] benzeneacet- amide methanesulfonate). Each possibility represents a separate embodiment of the present invention. According to some embodiments, the GIRK4 inhibitor is Tertiapin.

According to some embodiments, the immune disorder is selected from the group consisting of an autoimmune disease, an inflammatory disease and an autoinflammatory disease. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the immune disorder is autoimmune disease is multiple sclerosis (MS).

According to some embodiments, the subject is a human.

According to some embodiments of the methods described above for identifying a B cell as a regulatory B cell or as a B-la cell, the GIRK protein is detected with an antibody or an antigen-binding fragment thereof, an aptamer, or an inhibitor that specifically binds to the GIRK protein. Each possibility represents a separate embodiment of the present invention.

According to some embodiments, the GIRK protein is selected from the group consisting of a GIRKl protein, a GIRK2 protein, a GIRK3 protein and a GIRK4 protein. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the GIRK protein is a GIRK4 protein. According to some embodiments, the methods described above further comprise the step of detecting IL-10 secretion from the B cell following stimulation of the B cell with an agent that elicits an immune response.

According to some embodiments, the B cell is present in a biological sample. According to some embodiments, the biological sample is a liquid sample or a solid tissue sample. Each possibility represents a separate embodiment of the present invention.

According to some embodiments, the liquid sample is a blood sample or a liquid sample obtained from a body cavity. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the body cavity is the peritoneal cavity or the pleural cavity. Each possibility represents a separate embodiment of the present invention.

According to some embodiments, the solid tissue sample is derived from an immune organ selected from the group consisting of lymph node, spleen, bone marrow, Peyer's patch, tonsil and adenoid. Each possibility represents a separate embodiment of the present invention.

According to some embodiments, the RNA molecule is detected by a nucleic acid probe that specifically hybridizes to the RNA molecule.

According to some embodiments, the nucleic acid probe is a primer for amplifying the RNA molecule by a nucleic acid amplification method. According to some embodiments, the methods described above further comprise detecting IL-10 secretion following stimulation with an agent that elicits an immune response.

According to some embodiments, the agent that elicits an immune response is Lipopolysaccharide (LPS), Ionomycine, phorbol 12-myristate 13-acetate (PMA) or any combination thereof. Each possibility represents a separate embodiment of the present invention.

Further embodiments and the full scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows GFP-GIRK allele structure, derived from genomic DNA sequencing of GENSAT GFP mice.

Figure 2 shows micrographs demonstrating GFP expression in GIRK4-GFP mouse organs. A) Fluorescent binocular image of a whole heart. B) Confocal microscope image of a 350 μπι hippocampal slice. C) Fluorescent binocular image of a whole spleen. D) Fluorescent microscope image of a fixated spleen slice and a spleen structure scheme. E) Fluorescent binocular image of the femur. F) Two photon image of an inguinal lymph node.

Figure 3 demonstrates that GFP expression correlates with GIRK4 expression. A) FACS analysis of GFP expression pattern in splenocytes revealed two main cell populations with similar morphological properties: GFP expressing cells (circulated and designated as GFP), and non GFP cells (designated as control). B) RT-PCR of RNA extracted from splenocytes derived from wt, GIRK4 knockout mice (GIRK4^_/~ mice), and sorted cells (control and GFP). C) Western blot on membrane proteins extracted from GFP expressing cells (GFP) and non GFP cells (control). D) Electrophysiological recordings of a splenic GFP B cells treated with the GIRK4 blockers Tertiapin-Q (TPN) and BaCh.

Figure 4 shows FACS plots indicating GFP expression in splenic cells. Splenocytes extracted from GIRK4-GFP mice were stained with CDl lb, CDl lc, CD3, CD19 and CD41 fluorescent antibodies and analyzed using flow cytometry.

Figure 5 shows FACS analysis identifying GFP expressing splenic B cells. Splenocytes extracted from GIRK4-GFP mice were stained with CD21, CD24 and CD23 and analyzed using flow cytometry. A) Analysis of CD21/CD24 staining of GFP splenocytes in order to identify FO, Tl and T2+MZ cells. B) Analysis of CD21high/CD24high cells stained with CD23 in order to distinguish between MZ and T2 cells. Figure 6 demonstrates identification of GFP expressing B cells in the peritoneum. Peritoneal cells were extracted from GIRK4-GFP mice, stained with CD19, CD27, CDl lb, and CD5 markers and analyzed using flow cytometry. A) Peritoneal GFP cells stained with CD19, and CD27. B) CD19 expressing GFP cells stained with CD5 and CDl lb markers. C) GFP expression levels analyzed in B-la, B-lb, and B-2 cells.

Figure 7 illustrates analysis of IL-10 secretion in GFP expressing cells isolated from the peritoneum. A) IL-10 secretion analysis in stimulated and non stimulated GIRK4-GFP cells. B) IL-10 secretion analysis in GFP high and GFP low cells.

Figure 8 is a bar graph demonstrating GIRK4 mRNA expression following B cells stimulation. Peritoneal cells were stimulated for 6 hours with LPS, ODN and IgM, and as a control unstimulated cells (none). mRNA was extracted and quantified using real-time PCR. Results are expressed as percentage of RNA expression levels compared to the pretreated sample.

Figure 9 is a bar graph demonstrating B cells distribution in wt and GIRK4 knockout mice (GIRK4^_/~ ; ko). Cells extracted from the spleen, bone marrow, lymph nodes, and the peritoneal cavity were stained with CD 19 in order identify the B cells. In the right panel, peritoneal cells stained with CD5 and CD1 lb as well for B-l and B-2 populations' analysis.

Figure 10 shows bar graphs indicating that GIRK4 reduces B cell CXCL13-dependnet migration. A) A bar graph depicting the migration of GIRK4-transfected A20 B lymphoma cells in the presence or absence of 100 nM TPN and of GFP-transfected A20 B lymphoma cells (GIRK4 mock) B) A bar graph depicting the migration of peritoneal B lymphocytes (CD 19 positive) extracted from wt or GIRK4 knockout mice (GIRK4^_/~ ; ko).

Figure 11 shows bar graphs demonstrating GIRK4 dependant inhibition of migration of lymphocytes following stimulation with CXCL12. A) Migration of peritoneal B and T cells in wt and GIRK4 knockout mice (GIRK4^_/~ ; ko). B) Migration of sorted (using a magnetic bead sorting kit) and unsorted splenic T cells and of unsorted B cells in wt and GIRK4 knockout mice (GIRK4^7" ; ko).

Figure 12 shows bar graphs indicating that GIRK4 may be involved in B cells secretion of factors associated with migration. A) Migration of peritoneal cells following incubation with conditional media obtained from wt and GIRK4 knockout mice (GIRK4^_/~ ; ko) B cells that were either or not incubated with BFA. B) Migration of wt and GIRK4 knockout mice (GIRK4 ^/_ ; ko) peritoneal cells incubated with or without BFA treatment.

Figure 13 is a line graph demonstrating delayed EAE onset and reduced severity in GIRK4 knockout mice (GIRK4^_/~; K.O) as compared to wt mice (W.T).

Figure 14 is a line graph indicating that cells derived from activated GIRK4 knockout mice (GIRK4 ^/_ ; K.O) lymph nodes are not subjected to stimulation. Stimulation Index (S.I) - mean cpm in test cultures divided by mean cpm in control cultures.

Figure 15 is a line bar graph indicating that T cells' stimulation is less effective using APC originated in GIRK4 knockout mice (GIRK4^"/_ ; K.O) as compared to wt mice. Stimulation Index (S.I) - mean cpm in test cultures (in the presence of MOG35-55) divided by mean cpm in control cultures (without MOG35-55). Stimulation of T cell line with splenocytes obtained from wt and GIRK4^_/~ mice subjected to MOG35-55.

Figure 16 is a line graph indicating that GIRK4 blocker decreases antigen presentation activity. Stimulation Index (S.I) - mean cpm in test cultures divided by mean cpm in control cultures. Stimulation of T cell line with splenocytes obtained from wt mice subjected to MOG35-55 and treated with TPN.

Figure 17 is a line graph indicating that GIRK4 blocker do not change the stimulation of T cell line with splenocytes obtained from GIRK4^_/~, K.0 mice subjected to MOG35-55 and treated with TPN, as control.

Figure 18A is FACS plots showing that following depletion of CD 19 B cells by anti- mouse CD19 positive selection (EasySep Stem Cell catalog#18754) there are less than 10% CD19 positive cells in the remaining population (called B-). Figure 18B is a line graph indicating that knock out B- APCs stimulated the T-cells less efficiently than wild type B- APC. TPN decreased the stimulation index (S.I) of wild type B- APC, but did not change girk4 knock out B- APC activity. Figure 19 shows bar graphs indicating that knock out APCs secrete lower levels of

Interleukin 12 (IL-12) (naturally produced by dendritic cells and macrophages in response to antigenic stimulation) as compared to wild type APCs. This result indicates that APC originated from knock out mice are antigen presenting defected. Pre-incubation with TPN did not influence IL-12 secretion.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides, according to one aspect, a method of treating an immune disorder, inter alia, multiple sclerosis, comprising administering to a subject in need of such treatment a composition comprising GIRK4 inhibitor. According to a further aspect, the present invention provides methods of identifying B cell subtypes comprising detecting the presence of GIRK protein or of a polynucleotide sequence encoding GIRK protein in a biological sample.

As exemplified herein below, regulatory B cells, known as suppressors of the immune system, express G protein-coupled inwardly-rectifying potassium 4 channels (GIRK4). Further, stimulation and proliferation of T cells lacking GIRK4 protein was inhibited as compared to wt T cells. GIRK4 was found to regulate migration of both T and B cells. Finally, onset of clinical symptoms associated with brain inflammation in an Experimental Autoimmune Encephalomyelitis (EAE) mouse model were delayed in mice lacking GIRK4 protein.

Without wishing to be bound by any particular concept or mechanism of action, these findings indicate that GIRK plays an important role in immune system and particularly in mediating immune disorders.

Thus, the present invention provides, for the first time, a method of treating an immune disorder in a subject in need thereof, comprising the step of administering to the subject a therapeutically effective amount of at least one G protein gated Inward Rectifying K+ channel 4 (GIRK4) inhibitor, thereby treating the immune disorder. It is to be understood that GIRK is interchangeable with any alternative name or synonym of this protein known in the art. Typical synonyms of GIRKl include, but are not limited to, inward rectifier K(+) channel Kir3.1, and potassium channel inwardly rectifying subfamily J member 3. Typical synonyms of GIRK2 include, but are not limited to, inward rectifier K(+) channel Kir3.2, and potassium channel inwardly rectifying subfamily J member 6. Typical synonyms of GIRK3 include, but are not limited to, inward rectifier K(+) channel Kir3.3, and potassium channel inwardly rectifying subfamily J member 9. Typical synonyms of GIRK4 include, but are not limited to, Cardiac Inward Rectifier (CIR), Heart KATP channel, Inward rectifier K(+) channel Kir3.4 (IRK-4), KATP-1 , Potassium channel inwardly rectifying subfamily J member 5 and IKach. The term "treating" as used herein includes, but is not limited to any one or more of the following: delaying onset, decreasing severity, abrogating, ameliorating, inhibiting, attenuating, blocking, suppressing, reducing, halting, alleviating or preventing symptoms associated with an immune disorder.

The method of "treating an immune disorder" includes, but is not limited to, administration of a GIRK4 inhibitor to a subject in order to prevent the disorder, cure the disorder or to prolong the health or survival of the subject beyond that expected in the absence of such treatment.

The term "therapeutically effective amount" as used herein means that the amount of the GIRK4 inhibitor administered is of sufficient quantity to achieve the intended purpose, such as, in this case, treating an immune disorder in the patient.

According to some embodiments, the GIRK4 inhibitor inhibits GIRK4 activity in lymphocytes. According to some embodiments, the GIRK4 inhibitor is capable of reducing the overall expression of GIRK4. According to some embodiments, the GIRK4 inhibitor is capable of neutralizing the functionality of GIRK4. According to some embodiments, the GIRK4 inhibitor is capable of inducing GIRK4 degradation.

According to some embodiments, the expression "inhibiting GIRK4 activity" comprises any one or more of the following: attenuating, reducing or preventing cellular processes, pathways or phenotypes associated with GIRK4.

According to some embodiments, inhibiting GIRK4 activity is mediated by at least one or more of reducing, inhibiting or preventing the expression of GIRK4, neutralizing the functionality of GIRK4 and inducing GIRK4 degradation. According to some embodiments, inhibiting GIRK4 activity is mediated by reducing, inhibiting or preventing the expression of GIRK4. Inhibiting GIRK4 activity may be mediated directly by interacting with GIRK4 gene, mRNA or protein or indirectly by interacting with a gene, mRNA or protein associated with GIRK4-mediated activity or expression. According to some embodiments, expression is over- expression.

As used herein the term "expression" refers to the production of a functional end- product, e.g., an mRNA or a protein of a gene in a cell. As used herein the term "over- expression" is an expression of a gene above the expression level under normal conditions. By "normal conditions" it is meant a steady state condition wherein no pathological condition associated with immune disorder occurs and/or no medical intervention is required.

According to some embodiments, the lymphocytes are T cells. According to some embodiments, the lymphocytes are B cells. According to some embodiments, the B cells are selected from the group consisting of B-la cells, regulatory B cells (B IO cells), B-lb cells and B-2 cells. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the B cells are B- la cells.

According to some embodiments, the GIRK4 inhibitor is an antibody or an antigen- binding fragment thereof, capable of binding to GIRK4. Each possibility represents a separate embodiment of the present invention.

The term "antigen-binding fragment thereof as used herein refers to one or more fragments of an antibody which maintains/maintain the ability to specifically bind GIRK4.

According to some embodiments, the GIRK4 inhibitor is selected from the group consisting of Tertiapin (TPN, amino acid sequence ALCNCNRIIIRHMCWKKCGKK (SEQ ID NO: 7)), Charybdotoxin (CTX, amino acid sequence Pyr- FTNVSCTTSKECWSVCQRLHNTSRGKCMNKKCRCYS (SEQ ID NO: 8)), Bupivacaine ((R5)-l-butyl-N-(2,6-dimethylphenyl)piperidine-2-carboxamide), Ethosuximide, SCH23390 (R(+)-7-chloro-8-hydroxy-3-methyl-l-phenyl-2,3,4,5-tetrahydro-lH-3-benzazepine hydrochloride) and U50488H (trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(pyrrolidinyl)cyclohexyl]- benzeneacet-amide methanesulfonate). Each possibility represents a separate embodiment of the present invention. According to some embodiments, the GIRK4 inhibitor is Tertiapin.

As used herein the term "GIRK4 inhibitor" refers to an agent capable of inhibiting GIRK4 activity. According to some embodiments, the GIRK4 inhibitor is selected from the group consisting of a chemical agent or moiety, a protein, a polypeptide or a peptide, and a polynucleotide molecule. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the GIRK4 inhibitor is a GIRK family of proteins inhibitor. In accordance with those embodiments, the GIRK4 inhibitor is also capable of inhibiting at least one or more of GIRK1, GIRK2, and GIRK3. According to some embodiments, the GIRK4 inhibitor is specific to GIRK4 and is not capable of inhibiting other members of the GIRK family of proteins. According to some embodiments, the GIRK4 inhibitor is specific to the GIRK family and is not capable of inhibiting other ion channel proteins or other voltage-activated K+channels. According to some embodiments, the GIRK4 inhibitor is specific to the GIRK4 and is not capable of inhibiting other ion channel proteins or other voltage-activated K+channels.

According some embodiments, the polynucleotide molecule is a nucleic acid sequence or a molecule capable of hybridizing to nucleic acids encoding or controlling GIRK expression. Exemplary nucleic acid sequences suitable in the context of the present invention include, but are not limited to, a small hairpin RNA (shRNA) or a small interference RNA (siRNA) molecule, a micro RNA (miRNA) molecule and an antisense molecule. Each possibility represents a separate embodiment of the invention.

According to some embodiments, the GIRK4 inhibitor is a protein, a polypeptide or a peptide. The protein, polypeptide or peptide may be a synthetic or a recombinant protein, polypeptide or peptide. The protein, polypeptide or peptide may be a chimeric or fusion protein, polypeptide or peptide composed of at least two portions of a protein polypeptide or peptide. Although a number of protein inhibitors of voltage-activated K+channels are known, relatively few have been identified for the GIRK channels. One such peptide inhibitor contemplated for use in accordance with the present invention is isolated Tertiapin (TPN) or a derivative thereof. Known Tertiapins include, but are not limited to Tertiapin-Q and Tertiapin- LQ. Each possibility represents a separate embodiment of the invention. Other suitable peptide inhibitors include Charybdotoxin.

According to some embodiments, the GIRK inhibitor is a chemical agent or moiety. Exemplary chemical agents may include for example, without limitation, bupivacaine ((RS)- l-butyl-N-(2,6-dimethylphenyl) piperidine-2-carboxamide), ethosuximide ((RS)-3-ethyl-3- methyl-pyrrolidine-2,5-dione), ifenprodil (4-[2-(4-benzylpiperidin-l-yl)-l-hydroxypropyl]), SCH23390 (R(+)-7-chloro-8-hydroxy-3-methyl-l-phenyl-2,3,4,5-tetrahydro-lH-3- benzazepine hydrochloride), and U50488H (trans-(+/-)-3,4-dichloro-N-methyl-N-[2- (pyrrolidinyl)cyclohexyl] benzeneacetamide methanesulfonate). According to some embodiments, the chemical agent is an anti depressant drug, such as imipramine (3-(10,l l- dihydro-5H-dibenzo[b,f]azepin-5-yl)-N,N-dimethylpropan-l-amine), desipramine (3-(10, 11- dihydro-5H-dibenzo[b,f]azepin-5-yl)-N-methylpropan-l-amine), amitriptyline (3-(10,l 1- dihydro-5H-dibenzo[a,d]cycloheptene-5-ylidene)-N,N-dimethylpropan-l-amine), nortriptyline (3-(10,l l-Dihydro-5H-dibenzo[a,d]cyclohepten-5-ylidene)-N-methyl-l- propanamine), clomipramine (3-(3-chloro-10,l l-dihydro-5H-dibenzo[b,f]azepin-5-yl)-N,N- dimethylpropan-1 -amine), and maprotiline (N-Methyl-9,10-ethanoanthracene-9(10H)- propanamine). Each possibility represents a separate embodiment of the invention. According to some embodiments, the agent is specific for inhibition of one or more inhibitor of the GIRK family. According to some embodiment, GIRK4 inhibitor is any agent or moiety with GIRK4 blocking activity As used herein the term "Tertiapin" refers to a 21-amino acid protein derived from honeybee venom and inhibits GIRK 1 and 4 subunits and the renal outer medullary potassium 1 (ROMK1) channel with nanomolar affinities.

As used herein the term "immune disorder" relates to any disease, disorder or condition associated with the immune system. The term includes, but is not limited to, an autoimmune disease, an inflammatory disease, an autoinflammatory disease and transplant rejection of tissues.

The term "autoimmune disease" as used herein refers to a disease in which the production of antibodies and/or T cells directed against a self-antigen is a cause of the pathology of the disease. Within the scope of the present invention are autoimmune diseases such as, but not limited to, Multiple Sclerosis (MS), systemic lupus erythematosus, Sjogren's disease, type I diabetes, scleroderma, mixed connective tissue disease, primary biliary cirrhosis, autoimmune hemolytic anemia, autoimmune thyroiditis, idiopathic Addison's disease, vitiligo, gluten- sensitive enteropathy, Grave's disease, myasthenia gravis, idiopathic thrombocytopenia purpura, pemphigus vulgaris, Goodpasture's disease, bullous pemphigoid, rheumatoid arthritis, gouty arthritis, juvenile rheumatoid arthritis, nephritis, glomerulonephritis. Each possibility represents a separate embodiment of the invention. In one embodiment, the autoimmune disease is multiple sclerosis. The term "inflammatory disease", as used herein, refers to a disease, a condition or a disorder caused by, or resulting in inflammation that persists and results in an inflammatory state. Inflammation may be systemic or localized to particular tissues or organs. Inflammation may be caused in response to an injury or may be stimulated by a physical, a chemical, or a biologic agent. Inflammation may be caused as a result of perturbation of the cellular immune response that results in recognition of host proteins as foreign. Thus, the inflammatory response becomes misdirected at host tissues with effector cells targeting specific organs or tissues often resulting in irreversible damage. Often, inflammatory disease is characterized by an imbalance in the levels of T-helper (Th) subsets (i.e., Thl cells versus Th2 cells).

Examples of inflammatory diseases include, without limitation, Multiple Sclerosis (MS), sepsis, septic shock, endotoxic shock, Crohn's disease, ulcerative colitis, inflammatory diseases involving acute or chronic inflammation of bone and/or cartilage in a joint, polymyositis, anaphylactic reaction, asthma, conjunctivitis, inflammatory gum disease, pulmonary sarcoidosis, ocular inflammation, allergy, emphysema, ischemia-reperfusion injury, fibromyalagia, psoriasis and dermatitis. Each possibility represents a separate embodiment of the invention. In one embodiment, the inflammatory disease is multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the Central Nervous System (CNS) with varied clinical presentations and heterogeneous histopathological features. The underlying immunological abnormalities in MS lead to various neurological and autoimmune manifestations. As used herein the term "autoinflammatory disease" relates to a disease characterized by recurrent episodes of systemic inflammation in the absence of pathogens, autoantibodies or antigen specific T cells. These disorders are caused by primary dysfunction of the innate immune system, without evidence of adaptive immune dysregulation. Innate immune abnormalities include aberrant responses to pathogen associated molecular patterns (PAMPs) like lipopolysaccharide and peptidoglycan, prominent neutrophilia in blood and tissues, and dysregulation of inflammatory cytokines (IL-lbeta, TNF-alpha) or their receptors.

According to some embodiments, an autoinflammatory disease is selected from the group consisting of asthma, Familial Mediterranean Fever (FMF), Neonatal Onset Multisystem Inflammatory Disease (NOMID), Tumor necrosis factor Receptor Associated Periodic Ayndorome (TRAPS), Deficiency of the Interleukin-1 Receptor Antagonist (DIRA), and behcet's disease.

It is to be noted that some diseases, disorders or conditions are controversial as to their classification as autoimmune, autoinflammatory or inflammatory disease. For example, there is evidence that MS is, at least in part, an autoimmune-mediated disease. Other evidence suggests that this disease is a classical inflammatory disease. The present invention does not contend to classify diseases and is not limited to a particular category or classification of a particular disease, disorder or condition.

According to some embodiments, the immune disorder is subject is a human. The invention is also useful for reducing transplant rejection of tissues and organs such as, and without limitation, transplants of kidney, liver, heart, bone marrow and pancreas. The term "transplant rejection" refers to any one or more undesirable results, whether clinical or pathological or the like, that are associated with introducing a donor tissue to a recipient animal. Transplant rejection symptoms generally result from histocompatibility variations between donor and recipient that lead to stimulation of the recipient's immune system and/or to an inflammatory response against the donor tissue. The invention is useful for reducing one or more symptoms of a condition selected from autoimmune disease, inflammatory disease, autoinflammatory disease, and transplant rejection.

According to another aspect, the present invention provides a pharmaceutical composition comprising at least one GIRK4 inhibitor for use in treating an immune disorder. According to some embodiments, the present invention provides a pharmaceutical composition comprising as an active ingredient a GIRK inhibitor and a pharmaceutically acceptable carrier, excipient or diluent.

As used herein the term "pharmaceutical composition" refers to a preparation of one or more of the GIRK inhibitors described herein, with other components such as pharmaceutically acceptable carriers and excipients. The purpose of a pharmaceutical composition is to facilitate administration of a compound to a subject.

As used herein, the term "excipient" refers to an inert substance added to a pharmaceutical composition to further facilitate administration of the GIRK inhibitor. Examples, without limitation, of excipients include calcium carbonate, calcium phosphate, various sugars and types of starch, cellulose derivatives, gelatin, vegetable oils, and polyethylene glycols.

As used herein the phrase "pharmaceutically acceptable carrier" refers to a carrier, an excipient or a diluent that does not cause significant irritation to an organism and does not abrogate the biological activity and properties of the administered compound.

As used herein, the term "carrier" refers to any substance suitable as a vehicle for delivering of the GIRK inhibitor of the present invention to a suitable biological site or tissue. As such, carriers can act as a pharmaceutically acceptable excipient of the pharmaceutical composition of the present invention. Carriers of the present invention include: (1) excipients or formularies that transport, but do not specifically target a molecule to a cell (referred to herein as non-targeting carriers); and (2) excipients or formularies that deliver a molecule to a specific site in a subject or a specific cell (i.e., targeting carriers). Examples of non-targeting carriers include, but are not limited to water, phosphate buffered saline, Ringer's solution, dextrose solution, serum-containing solutions, Hank's solution, other aqueous physiologically balanced solutions, oils, esters and glycols. Aqueous carriers can contain suitable auxiliary substances required to approximate the physiological conditions of the recipient, for example, by enhancing chemical stability and isotonicity.

Pharmaceutical compositions of the present invention may be sterilized by conventional methods. The term "targeting carriers" is interchangeable with the term "delivery vehicles". Delivery vehicles according to the present invention include agents that are capable of delivering the GIRK inhibitor of the present invention to a target site in a subject. A "target site" refers to a site in a subject to which one desires to deliver the GIRK inhibitor. Examples of delivery vehicles include, but are not limited to, artificial and natural lipid-containing delivery vehicles. Natural lipid-containing delivery vehicles include cells and cellular membranes. Artificial lipid-containing delivery vehicles include liposomes and micelles. A delivery vehicle of the present invention can be modified to target a particular site in a subject, thereby targeting and making use of the GIRK inhibitor of the present invention at that site. Suitable modifications include manipulating the chemical formula of the lipid portion of the delivery vehicle and/or introducing into the vehicle a compound capable of specifically targeting a delivery vehicle to a preferred site, for example, a preferred cell type or tissue.

According to some embodiments, the composition comprising a GIRK inhibitor may further comprise an additional agent. The additional agent may be any treatment for an immune disorder.

According to the present invention, treating immune disorder comprises administering at least one GIRK inhibitor to a subject in need thereof.

The term "subject" includes humans, and animals amenable to therapy with a GIRK4 inhibitor or humans, and animals afflicted with an immune disorder. According to some embodiments, the subject is a human subject.

The term "subject" as used herein, includes, for example, a subject who has been diagnosed to be afflicted with an immune disorder or a subject who has been treated to ameliorate an immune disorder, including subjects that have been refractory to the previous treatment. Also encompassed within the present invention is a healthy subject having a risk of being affected with a disorder a disease or a condition associated with an immune disorder.

The GIRK4 inhibitor of the present invention may be administered systemically or locally. Non limiting examples of systemic routes include intravenous, intraarterial, intraperitoneal, and subcutaneous routes. According to some embodiments, the GIRK4 inhibitor is administered locally into the tissue associated with an immune disorder. According to some embodiments, the tissue is a brain tissue, and the administration route is directly into the brain tissue.

The administered dose of the GIRK4 inhibitor in the method of the present invention may be determined while taking into consideration various conditions of a subject that requires treatment, for example, the severity of symptoms, general health conditions of the subject, age, weight, sex of the subject, diet, the timing and frequency of administration, a medicine used in combination, responsiveness to treatment, and compliance with treatment.

According to some embodiments, treating an immune disorder comprises administering to a subject in need thereof a plurality of GIRK inhibitors.

The frequency of administration depends on the properties of the GIRK4 inhibitor used and the above-mentioned conditions of the subject and may be, for example, a plurality of times a day (e.g. 2, 3, 4, 5, or more times per day), once a day, every few days (e.g. every 2, 3, 4, 5, 6, or 7 days, etc.), once a week, or once every few weeks (e.g. once every 2, 3, or 4 weeks, etc.).

According to another aspect, the present invention provides a method of identifying a B cell, comprising detecting the presence of GIRK protein or of a polynucleotide sequence encoding GIRK protein in a biological sample. The invention is based on the discovery that regulatory B cells and B l-a cells express GIRK4 protein.

As used herein the term "B lymphocyte(s)" is interchangeable with the term "B cells" and refers to a group of white blood cells/lymphocytes that play a vital role of the immune system. The principal functions of B cells are to produce antibodies against antigens, to perform the role of antigen-presenting cells (APCs), and to develop into memory B cells after activation by antigen interaction.

B lymphocytes are developed in the bone marrow from lymphoid stem cells. During early development, the immunoglobulin (Ig) gene undergoes rearrangement, in order to create a wide variety of foreign antigen recognizing antibodies. After gene rearrangement is completed, the B cell receptor (BCR) is expressed. During the development process, B lymphocytes undergo several checkpoints confirming the proper rearrangement of the Ig genes, and the functionality of the BCR. The surviving B cells, termed immature, are ready to start their maturation process in the spleen. B cell maturation eventually yields two main cell types, termed according to their location in the spleen: the Marginal Zone cells (MZ) and the Follicular Cells (FO). MZ cells remain in the spleen and are involved in the T cell independent humoral response, whereas FO B lymphocytes leave the spleen and migrate to the periphery through the blood and lymphatic vessels and are termed naive B cells. The naive B lymphocytes scan for foreign antigens that will bind the IgM receptor they express. These antigens can be soluble factors such as toxins or small pathogens. Once a B cell binds an antigen, it internalizes and then presents its fragments on its Major Histocompatibility Complex Class II (MHC II) receptor. The specific MHC II cells then migrates to a lymph node where they undergo activation by T helper cells with the corresponding receptor. The B cell begins to proliferate and has two possible fates: it can either differentiate to become an antibody secreting cell termed plasma cell, or become a memory cell - a long living cell for a quicker future response to the same antigen. These cells continue to circulate in the blood. The plasma cells start secreting antibodies to overcome the pathogen. The humoral response, briefly described above, has many participating receptors and signaling factors, both intra and extracellular. Those cells described above are also referred to "the classical B cells" and are interchangeable with the terms "B-2 cells" and B-2 lymphocytes".

As used herein the term "B-1 cells" is interchangeable with the term "B-1 lymphocytes" and refers to B-1 cells that express IgM in greater quantities than IgG and their receptors show polyspecificity, meaning that they have low affinities for many different antigens. Polyspecific immunoglobulins often have a preference for other immunoglobulins, self antigens and common bacterial polysaccharides. B-1 cells are present in low numbers in the lymph nodes and spleen and are instead found predominantly in the peritoneal and pleural cavities. B-1 cells are divided into two main subgroups: B-la and B-lb, distinct from each other and from classic B-2 lymphocytes by several membrane markers. B-1 cells develop in the fetus liver and then migrate mostly to the body cavities, but also to the spleen (B-lb cells) where they continue to proliferate. B-la and B-lb cells produce natural antibodies and have an important role in defense against common pathogens. As used herein the term "regulatory B cells" is interchangeable with the terms "B IO" and "Breg" and relates to B cells or lymphocytes that can negatively regulate the immune response by producing regulatory cytokines and directly interacting with pathogenic T cells via cell-to-cell contact. These B lymphocytes reside mostly, but not only, in the peritoneal cavity and secrete IL-10 upon stimulation. Regulatory B cells modulate several autoimmune and inflammatory diseases such as multiple sclerosis (MS). Although some attempts were made to classify and categorize the different regulatory B cells according to membrane markers, origin or way of activation, to date there is no unified model that allows their full characterization. According to some embodiments of the methods described above for identifying a B cell as a regulatory B cell or as a B- la cell, the GIRK protein is detected with an antibody or an antigen-binding fragment thereof, an aptamer, or an inhibitor that specifically binds to the GIRK protein. Each possibility represents a separate embodiment of the present invention.

According to some embodiments, the GIRK protein is selected from the group consisting of a GIRK1 protein, a GIRK2 protein, a GIRK3 protein and a GIRK4 protein. Each possibility represents a separate embodiment of the present invention. According to some embodiments, the GIRK protein is a GIRK4 protein.

According to some embodiments, the methods described above further comprise the step of detecting IL-10 secretion from the B cell following stimulation of the B cell with an agent that elicits an immune response.

According to some embodiment, the method of identifying regulatory B cells or B-la cells further comprises detecting secretion of IL-10 following stimulation with an agent that elicits an immune response. According to some embodiments, "an agent that elicits an immune response" refers to any agents that triggers a chain of events associated with the immune systems and which leads to an immune response. According to some embodiment, an agent that elicits an immune response is at least one or more of Lipopolysaccharide (LPS), Ionomycine, phorbol 12-myristate 13-acetate (PMA). According to some embodiments, the agent that elicits an immune response is a combination of LPS, Ionomycine, and PMA. According to some embodiments, the LPS is provided at a concentration within the range of 1 g/ml to 50 μg/ml. According to one embodiment, the LPS is provided at a concentration of 10 μg/ml. According to some embodiments, the Ionomycine is provided at a concentration within the range of 1 nM to 1000 nM. According to one embodiment, the Ionomycine is provided at a concentration of 700 nM. According to some embodiments, the PMA is provided at a concentration within the range of 1 to 1000 nM. According to one embodiment, the PMA is provided at a concentration of 300 nM. According to some embodiments, the method of identifying B-la cells further comprises detecting CD5 expression. According to some embodiments, the method of identifying B-la cells further comprises detecting CD l ib expression.

According to some embodiments, the B-la cells and B regulatory cells express higher levels of GIRK as compared to other B cell types or to other non B cell types. According to some embodiments, GIRK expression level in the B-la cells and B regulatory cells is higher by at least 1.2, 1.4, 1.6, 1.8, 2, 3, 4, or 5 fold as compared to the expression level of GIRK in other B cell types or in other non B cell types. According to some embodiments, the term "other B cell types" refers to B-2 cells or to memory B cells. According to some embodiments, the term "other non B cell types" refers to cells, other than B cells, that are known to be negative for GIRK expression.

The methods of the invention may be carried out using various assay systems and methods for detection the GIRK protein or a polynucleotide encoding GIRK protein in a test biological sample. Suitable systems include those employing an immunoassay, a nucleic acid hybridization assay, or a combination thereof. Immunoassays for detecting a particular protein are known in the art and include for example, radioimmunoassay, (RIA), fluorescent immunoassay, (FIA) enzyme-linked immunosorbant assay (ELISA), immunohistochemistry (IHC) and flow cytometry based assays such as fluorescent activated cell sorting (FACS). Immunoassays can also be employed histologically to detect GIRK expression in a tissue sample. Tissue sample detection of GIRK can be accomplished by removing a histological sample from a subject, and contacting the sample with a labeled antibody. The antibody is typically contacted with the sample by overlaying the labeled antibody onto the sample. Through the use of such a procedure, the presence of GIRK can be determined and/or the distribution of the antigen in the histological sample can be examined. Those of ordinary skill in the art will readily appreciate that any of a wide variety of histological methods (such as staining procedures) can be modified in order to achieve such in tissue detection. Hybridization assays generally comprise contacting a sample containing nucleic acids (target nucleic acids) with a nucleic acid probe capable of hybridizing to GIRK nucleic acids, under conditions such that hybridization can occur, and detecting or measuring any resulting hybridization. Suitable hybridization assays include, for example, Northern blots, qualitative RT-PCR, and quantitative RT-PCR (also known as real-time PCR). GIRK nucleic acids can be used as probes and/or primers for such procedures.

According to some embodiments, the B cell is present in a biological sample.

According to some embodiments, the biological sample is a liquid sample or a solid tissue sample. Each possibility represents a separate embodiment of the present invention.

According to some embodiments, the liquid sample is a blood sample or a liquid sample obtained from a body cavity. Each possibility represents a separate embodiment of the present invention.

According to some embodiments, the body cavity is the peritoneal cavity or the pleural cavity. Each possibility represents a separate embodiment of the present invention.

According to some embodiments, the solid tissue sample is derived from an immune organ selected from the group consisting of lymph node, spleen, bone marrow, Peyer's patch, tonsil and adenoid. Each possibility represents a separate embodiment of the present invention. The methods of the invention are employed on a biological sample. As used herein the term a "biological sample" encompasses a variety of types of biological materials that can be used in the methods of the invention so long as the sample comprises B cell(s). The term encompasses tissue samples, derived from immune organs in which B cells reside. According to some embodiment, the immune organ is selected from the group consisting of lymph node, spleen, bone marrow, Peyer's patch, tonsil and adenoid. The term also encompasses blood and other liquid samples of biological origin, such as, lymph node aspirate, and body cavity contents. The term encompasses samples that have been manipulated in any way after their procurement, such as by lysis, treatment with reagents, solubilization, or enrichment for certain components. Also included are cells in cell culture, and cell lysates. It is to be explicitly understood that in accordance with the invention, a biological or test sample may be obtained i.e. removed, from the body of a subject, or accessed in vivo, for example by contacting with a specific reagent or apparatus.

As used herein, a biological sample that is "obtained from a subject", means that the sample is removed from the body of the subject, and any subsequent analysis thereof may be performed outside the body for example under in vitro or ex vivo conditions.

According to yet another aspect, the present invention provides a method for identifying a B cell as a regulatory B cell or as a B-la cell, comprising the step of detecting the presence of an RNA molecule encoding a GIRK protein in the B cell. According to some embodiments, the RNA molecule is detected by a nucleic acid probe that specifically hybridizes to the RNA molecule.

According to some embodiments, the nucleic acid probe is a primer for amplifying the RNA molecule by a nucleic acid amplification method.

According to some embodiments, the methods described above further comprise detecting IL-10 secretion following stimulation with an agent that elicits an immune response.

According to some embodiments, the agent that elicits an immune response is Lipopolysaccharide (LPS), Ionomycine, phorbol 12-myristate 13-acetate (PMA) or any combination thereof. Each possibility represents a separate embodiment of the present invention. The present invention further provides, in an aspect, a kit for the treatment of an immune disorder, comprising a pharmaceutical composition comprising at least one GIRK4 inhibitor and a carrier; and instruction for use of the pharmaceutical composition for the treatment of the immune disorder.

The present invention further provides, in an aspect, a kit for identifying a B-cell as a regulatory B cell or as a B-la cell, the kit comprising an agent capable of identifying the presence of a GIRK protein in the membrane of the B cell; and instruction for use. The present invention further provides, in an aspect, a kit for identifying a B-cell as a regulatory B cell or as a B-la cell, the kit comprising an agent capable of identifying the presence of a RNA molecule encoding a GIRK protein in the B cell; and instruction for use.

The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without undue experimentation and without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The means, materials, and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention.

EXAMPLES

EXAMPLE 1 - Novel identification of tissues expressing GIRK4. In order to identify body tissues expressing GIRK4, Tg(Kcnj5-EGFP)49Gsat C57B16J

(GIRK4 GFP) mice were utilized. GIRK4-GFP mice were obtained following Tg(Kcnj5- EGFP)49Gsat mouse line breeding with C57B16J for 10 generations to generate isogenic C57B16J wt GFP strain. Genotyping was performed on DNA extracted from mice tail tips using the GIRK4-GFP primers: 5' ATTTTAATTCACTGTATCTCAGC 3' (SEQ ID NO: 1), and 5' GTCCTTGAAGAAGATGGTG 3' (SEQ ID NO: 2). All assays were performed on adult mice at the age of 6-8 weeks. Figure 1 depicts GFP-GIRK allele structure derived from genomic DNA sequencing of GENSAT GFP mice.

Tissues expressing GIRK4 were identified using fluorescence microscopy. Since GIRK4 is known to be expressed in the atria and in intermediate hippocampal neurons in the molecular layer of the dentate gyrus, GFP expression in those tissues served as confirmation of detection specificity of GIRK4 expression (Figure 2; panels A-B). GFP expression was also observed in the spleen, inguinal lymph nodes (Figure 2; panels C and F) and in the bone marrow, but not in the thymus (data not shown). In the spleen, fluorescence microscopy images of ΙΟμπι histochemical spleen slices, showed a differential expression of several cell types in a ring shaped pattern correlating with the red pulp structure, known to host B cells (Figure 2; panel D). This data suggests that GIRK4 is present in cells of the immune system.

EXAMPLE 2 - Correlation between GIRK4 and GFP expression

Following detection of GFP expression in the spleen and bone marrow, but not in the thymus, the cell types expressing GFP in the spleen were characterized. Fluorescence Activated Cell Sorting (FACS) analysis was performed on splenocytes extracted from GIRK4-GFP mice. FACS was performed using FACSAria. Data analysis was done using FACSdiva (BD biosciences), FCSexpress (De-Novo software) and/or in-house written MatLab program. Splenic cells were extracted by mechanically rubbing spleen on a 40μπι cell nylon strainer (BD Falcon), followed by hypotonic pressure using RBC buffer (155mM NH4CI, lOmM KHCO3, ImM EDTA) and washing with PBS without CaCk and MgCk (PBS^" ^/_, Biological industries). Cells were suspended in PBS^_/" containing 2% BSA to a concentration of approximately 50x10⁶ cells/ml. The cells were loaded to the FACS and GFP expressing cells were sorted. In parallel, non-GFP-expressing cells with the same forward scatter (FSC) and side scatter parameters (SSC) served as a control.

The results demonstrated two main expression patterns of GFP with similar morphological properties: GFP expressing cells (circulated and designated as GFP), and non GFP cells (designated as control). In addition, fragment sized cells expressing high GFP levels were detected (Figure 3; panel A). In order to verify that indeed GFP expression correlates with GIRK4 expression, RT-

PCR analysis on RNA extracted from the sorted cell populations, namely from the lymphocyte sized GFP positive cells (GFP) and from the lymphocyte sized non GFP cells (control) was performed. RNA was extracted from lymphocytes using tri-reagent (Peqlab) and RNAeasy kit (Qiagen). The results indicated that only GFP expressing cells contained GIRK4 mRNA. In addition, mRNA extracted from splenocytes of wt animals was also positive to GIRK4 mRNA and served as positive control. mRNA extracted from GIRK4 knockout mice (GIRK4^_/~) served as a negative control (Figure 3; panel B).These results indicate that the transcription of GIRK4 channel gene occurs naturally, independent of the genetic manipulation made to produce the GIRK4-GFP mice. Western blot analysis was also performed to assess GIRK expression. Briefly, membrane proteins were extracted from atrial tissue and lymphocytes as follows: cells/tissue was homogenized in hypotonic buffer (50mM Tris, 2.5mM MgCk, ImM EGTA pH 7.8). Nuclei and cell fragments were spun down and the membrane fraction was extracted using ultracentrifugation (150,000 g). Membranes were suspended in lysis buffer (20mM Tris, 137mM NaCl, 10% Glycerol, 0.1% SDS, 0.5% Deoxylate, 1% Triton, 2mM EDTA, DNAse and protease inhibitors (Roche) pH 7.4). The membrane proteins were subjected to SDS- PAGE followed by western blot with anti-GIRK4 antibodies (Alomone Labs or Santa Cruz).

The western blot results confirmed that GIRK4 mRNA is also translated (Figure 3; panel C).

In order to assess GIRK4 activity in GFP expressing cells, electrophysiological recordings were performed on GFP expressing splenic cells using the whole-cell variation of the patch clamp technique. Recordings were performed on freshly isolated GFP positive B lymphocytes extracted from mouse spleen. The following solutions were used: Pipette solution (intracellular): lOmM KC1, 150mM, KF 2mM MgCl₂, lOmM HEPES, lOmM EGTA. The solution was brought to pH 7.2 with KOH. Low potassium bath solution (extracellular): 140mM NaCl, 5.6mM KC1, 1.2mM MgCk, 2.6mM CaCk, 5mM HEPES. The solution was brought to pH 7.4 with NaOH. High potassium bath solution (extracellular): 140mM KC1, 1.2mM MgCk, 2.6mM CaCk, 5mM HEPES. The solution was brought to pH 7.4 with NaOH. Cells were held at -80 mV and current recording signals were monitored continuously. Cells were treated mostly with several G protein coupled receptor (GPCR) ligands such as CXCU2 (lOOng/ml) and with GIRK blockers such as Tertiapin-Q (TPN) (100 nM) and BaCk (3mM).

Although currents were recorded from a very small portion of the GFP cells (approximately 5%), apparent basal inward potassium currents where detectable indicating sensitivity to TPN and BaCk (Figure 3; panel D). In view of the above, it may be determined that GFP positive cells express functional GIRK4 channels.

EXAMPLE 3 - characterization of cell types in the spleen that express GIRK4.

Splenocytes extracted from GIRK4-GFP mice were stained with different immune cell type-specific markers and analyzed using flow cytometry. Two main populations of GFP expressing cells were identified, the first one of small particles expressing high GFP that correlated with CD41 expression, indicated as platelets, and a second population of approximately 5% of the total lymphocytes expressing low GFP levels that correlate with CD 19 (a general marker for B cells) expression. These results suggest of the presence of the expression of GIRK4 channels in B lymphocytes. No correlation was detected with CD3 and CDl lc, and little correlation was observed with CDl lb, indicating that GIRK4 is not expressed in T lymphocytes and myeloid cells, respectively (Figure 4).

B cells mature in the spleen, accordingly the spleen hosts B cells in different developmental stages and types. Next, evaluation of the specific B cell lineages that express GFP was conducted using CD19. Splenic cells were stained with various immune markers for the different B-cell subpopulations and developmental stages in the spleen, and were correlated with the GFP signals. The results show that GFP is expressed in 21 ±2 of the splenic B cells. GFP was found in 21 ±2 of the T2, 20 ±2 of the marginal zone (MZ) and 22 ±2 of the follicular B cells (FO), and was hardly detected in Tl cells (Figure 5). These results suggest that GIRK4 is differently expressed in mature B cell populations. EXAMPLE 4 - characterization of cells type in the peritoneal cavity that express GIRK4.

The differential expression of GFP among the B cells subpopulations was determinded. Peritoneal cells were extracted by peritoneal flush with PBS^_/", stained and analyzed for the local B cell populations. Similar to the spleen, the peritoneum was found to contain lymphocyte sized cells expressing GFP; however GFP expression was detected in discrete subpopulations (Figure 6; panel A). In general, GFP expressing cells in the peritoneum were more abundant than in the spleen population and comprised 54 ±3 of the total B cell population. Further identification of the subpopulation of B lymphocytes revealed that 92% of the B-la cells were found to express high levels of GFP, whereas 65%±4 of the B-lb cells expressed medium levels of GFP and 36%±5 of the B-2 cells expressed low levels of GFP (Figure 6; panels B and C). Memory B cells, which develop only after B cell activation, showed no GFP expression (Figure 6; panel A).

Regulatory B lymphocytes are identified by their unique ability to secrete IL-10 following stimulation (DiLillo, D. J., et al. (2010) Ann. N Y Acad. Sci., 1183:38-57). In order to determine whether GFP is expressed in these cells, IL-10 secretion from the cells was analyzed. Briefly, IL-10 detection was performed using a cytokine secretion kit (Miltenyl Biotec). Peritoneal cells were extracted and stimulated with LPS (10μg/ml), Ionomycine (700 nM) and PMA (300 nM), and incubated for 5 hours at 37°C. The cells were then washed and incubated with a CD45-IL-10 double headed antibody for 5 min at 4°C followed by a wash and incubation for 45 minutes at 37°C. The cells were then washed and stained with anti-IL- 10 antibodies for 5 min and analyzed by flow cytometry.

The analysis revealed strong correlation between GFP expression and IL-10 secreting cells, mainly in the high GFP expressing cells. These results indicate that GFP is also expressed in regulatory B cells (Figure 7). The above results suggest that GIRK4 is expressed in mature B cells, mostly in the peritoneum, with enriched population of IL-10 secreting cells.

EXAMPLE 5 - down regulation of GIRK4 expression upon B cell activation.

B cells keep changing during their development, and as a result, their membrane protein expression profile is also altered. As indicated above, GFP expression, which correlates with GIRK4 expression in the GIRK4-GFP mice, is found in mature cells mostly in the peritoneal cavity. Next, the effect of B cell activation on GFP expression was determined. Accordingly, B lymphocytes were activated in vitro with LPS (20μg/ml, TLR4 activator), ODN (5μg/ml, TLR9 activator) and IgM (^g/ml, BCR activator) for 6 hours, and GIRK4 mRNA levels were measured following each one of the treatments using real-time PCR. RNA was extracted from lymphocytes using tri-reagent (Peqlab) and RNAeasy kit (Qiagen). cDNA was prepared using RT PCR with random primers (Applied Biosystems). Realtime PCR was performed using SYBR green (Applied Biosystems) with GIRK primers and HPRT1 as endogenous control, using the primers: GIRK4 5' GATGTCTCGTGCTCAACTGGAA 3' (SEQ ID NO: 3) and 5' GGCAAGTCATGCCTGTTGCT 3' (SEQ ID NO: 4), HPRT1 5' AGCAGTACAGCCCCAAAATG 3' (SEQ ID NO: 5) and 5' GGCCTGTATCCAACA CTTCG 3' (SEQ ID NO: 6).

GIRK4 mRNA levels dramatically decreased 6 hours following activation, by the various ligands (Figure 8). These results suggest that GIRK4 plays a role in mature naive cells. Accordingly, the processes that occur in naive mature B cells were focused and further assessed. EXAMPLE 6 - GIRK4 plays a role in B cell migration.

Like chemokine receptors, GPCRs that are linked to GIRK channels activation utilize the Gi/o G protein subfamily. This fact makes GIRK4 a natural candidate as a chemokine receptor downstream effector. Since chemokine receptors are in part responsible for the migratory action of lymphocytes, GIRK4 involvement in this process was assessed. The distribution of B cells in several lymph nodes (inguinal, mesenteric, axial and cervical), bone marrow and spleen was compared between wt and GIRK4^_/~ mice.

B cells distributions were found to differ in the presence and absence of GIRK4 channels. In GIRK4^_/~ mice, CD 19 expressing B lymphocytes showed a 31% increase in distribution in splenic and 35% in the bone marrow population, yet a 32% decrease in inguinal and 19% in cervical lymph nodes. Mesenteric and axial populations showed no significant difference between the two mice strains (Figure 9). When total peritoneal B cell populations were compared, no significant difference was observed, however, when B-l and B-2 populations were compared, a 40% decrease in B-2 distribution and 67% increase in B-la population was seen, with no change in B-lb population (Figure 9). The results thus indicate that GIRK4 channels may be involved in B cell migration, or, alternatively, may be involved in development or proliferation of these cells.

In order to distinguish between these two possibilities, a murine B cell lymphoma cell line, A20, which does not express GIRK4 channels was used. A migration assay was performed. Briefly, approximately cells 500,000 cells were plated onto the filter in the top well of 5μπι transwell plates (Costar). The bottom well contained RPMI medium with BSA (2%) plus treatment (CXCL13 gradient (up to 2μg/ml) and/or blocker). Cells were incubated for 4 hours at 37°C with the treatment. Next, the cells were stained with proper antibodies for B cell detection and analyzed by flow cytometry. Migration rates were calculated by counting cells at a constant volume, as a fraction of the total loaded cells. Rates were corrected for nonspecific passive migration in wells that did not contain the chemokine.

GIRK4 transfected A20 cells had 44% reduced migration rate compared to GFP transfected cells. Migration rates were calculated by counting cells at a constant volume, as a fraction of the total loaded cells. Rates were corrected for non-specific passive migration in wells that did not contain the chemokine. This difference in migration rate was abolished when GIRK4 transfected cells were treated with the specific channel blocker TPN (100 nM). Likewise, A 78% increase in migration rate of GIRK4 expressing A20 cells was observed in the presence of TPN (Figure 10; panel A), compared to GIRK4 expressing cells in the absence of TPN. This observation suggests that GIRK4 may play a role in B lymphocyte migration. To further investigate this hypothesis, peritoneal cells were extracted from wt and GIRK4^_/~ mice and CXCL13- dependent migration was tested with and without TPN. Indeed, peritoneal cells extracted from GIRK4^_/" showed a 100% increase in migration rate compared to peritoneal cells extracted from wt mice. Furthermore, when the migration assay was performed in the presence of 100 nM TPN, a 77% increase in migration rate was seen in wt cells with no significant effect on GIRK4^_/" peritoneal cells (Figure 10; panel B). These results further indicate that GIRK4 plays a role in B lymphocytes migration.

EXAMPLE 7 - GIRK4 may be involved in paracrine regulation of migration.

Previous studies have shown that GIRK channels are involved in insulin secretion in the pancreas (Iwanir, S. and E. Reuveny (2008) Pflugers Arch. 456(6): 1097-108). As shown above, GIRK4 is expressed in regulatory B lymphocytes. This raises the option that GIRK4 may be involved in paracrinic regulation of B cell migration. Thus, migration rate of wt and GIRK4^_/" B and T lymphocytes obtained from the peritoneum following incubation with CXCL12 was analyzed. The data indicated that GIRK4^"7" B lymphocytes displayed an increase of 52% in migration, while GIRK4^_/~ T lymphocytes (that do not express GIRK4) displayed a 90% increase (Figure 11 ; panel A).

Although the results shown above indicate that T cells extracted from GFP mice do not express GFP and accordingly do not express GIRK4 (Figures 2 and 3), it is possible that an undetected very low GFP expression exists in those cells. In order to elucidate whether this increase in T cell migration originates from paracrinic secretion, splenic T cells were sorted using negative selection magnetic beads (R&D Systems), underwent CXCL12 transwell migration assay and compared to total migrated splenocytes.

Although the spleen contains a different population of lymphocytes then the peritoneum, it has a relatively rich population of T cells compared to the peritoneum. Differently from the peritoneal B cells, in the spleen a 33% reduction was seen in the GIRK4^_/~ unsorted fraction, and no difference was seen the wt and GIRK4^_/~ T cells in the unsorted fraction. In the T cell sorted fraction, however, a 46% increase was seen in the GIRK4^_/~ sorted T cell fraction, indicating that T cells are affected by GIRK4 expression in other splenocytes (Figure 11 ; panel B). The results above indicate that lymphocytes that do not express GIRK4 can also be affected by the absence of the channel in B cells. These results suggest a possible soluble factor secreted by GIRK expressing B cells, or cell-cell interaction which affects migration.

Next, CXCL13-dependnet transwell migration assay was performed with wt peritoneal cells in the presence of various conditioned media. The cell-free conditioned media was obtained following 4 hrs in culture of wt and GIRK4^_/~ peritoneal cells in the presence or absence of the secretion blocker Brefeldin A (BFA).

A 40% decrease in migration was demonstrated in peritoneal cells incubated with medium obtained from GIRK4^_/~ B cells as compared to migration with wt B cells conditioned media (Figure 12; panel A). In order to evaluate whether blockage of secretion has a different effect following GIRK4 blockage, a migration assay was done in the presence and absence of BFA treatment in wt and GIRK4^_/~ cells. Here, a 27% increase was seen in migration following BFA treatment in wt cells, while no significant change was observed in GIRK4^_/~ cells (Figure 12; panel B). The GIRK4^_/~ increase in migration rate was reduced from 74% to 29%, indicating that secretion blockage with BFA reduces GIRK4's effect on CXCL13 dependant migration.

EXAMPLE 8 - GIRK4 alters antigen presenting activity.

Multiple Sclerosis (MS) has been shown previously to be delayed both by IL-10 secreting B cells, and by low levels of B2 cells (Krumbholz, M., et al. (2012) Nat. Rev. Neurol. 8(11): 613-23). As shown above, GIRK4 is expressed in IL-10 secreting cells (Figure 7), and GIRK4^_/~ mice display a different B cell distribution pattern then wt mice (Figure 10). In order to evaluate if the absence of GIRK4 indeed has a similar effect on MS progression, the EAE model was applied on wt and GIRK4^_/~ mice. C57B1/6J female mice were injected subcutaneously at one site in the flank with 200 μΐ of emulsion containing 100 μg of Myelin oligodendrocyte glycoprotein (MOG35-55) in CFA containing 300 μg Mycobacterium tuberculosis H37Ra ("classical" EAE). MOG is a well-recognized target antigen in MS and injection of a peptide mimicking MOG (MOG35-55) to mice causes EAE leading to gradual paralysis and finally to death. GIRK4^_/~ (n=8) and wt (n=13) female mice were induced for EAE using MOG35-55. Mice received 300 ng pertussis toxin in 500 μΐ PBS intra peritoneal immediately and 48 hours after immunization. Following the encephalitogenic challenge, mice were observed and scored. The mice were followed and scored daily on a scale of 0-6: 0= no clinical signs, 1= loss of tail tonicity, 2= flaccid tail, 3= hind leg paralysis, 4=hind leg paralysis with hind body paresis, 5= hind and foreleg paralysis and 6= death.

Both strains showed clinical signs, but the progression was significantly different. Clinical signs were shown earlier in wt as compared to GIRK4^_/~ mice. GIRK4^_/~ mice also displayed lower mean clinical severity than wt mice (Figure 13).

Next, GIRK4^_/" and wt mice were injected in the foot pad with MOG35-55. 10 days afterwards the draining lymph nodes were removed and subjected to ex-vivo stimulation assay with 1, 2.5 and 5μg MOG35-55. The stimulation of GIRK4^_/~ lymph nodes cells was insufficient as compared to wt lymphocytes (Figure 14). This result is consistent with the delayed and less severe EAE in GIRK4^_/" mice.

To assess which cells are responsible for the reduction in proliferation of GIRK4^"7" lymph node cells, T cell line was stimulated with APC harvested from wt and GIRK4^_/~ mice, at the presence of 1, 2.5 and 5 μgMOG35-55.

The T cell proliferation was significantly lower when the APC were originated in GIRK4^_/" mice compared to wt mice, suggesting that GIRK4^_/~ APC's are deficient in their antigen presenting capacity (Figure 15). Any changes seen in GIRK4^_/~ mice may not be related directly to the GIRK4 deficiency. In order to relate the findings to GIRK specifically, the stimulation assay was repeated using only wt APC, with the addition of GIRK4 blocker. The results showed that incubation of APC with TPN decreased the proliferation of the stimulated T cells (Figure 16). These results support the hypothesis that the absence of GIRK4 or its selective block decrease antigen presentation activity and may thus explain the delayed onset of EAE in GIRK4^_/~ mice as shown above. Figure 17 further affirms that conclusion. EXAMPLE 9 - B cell-depleted cell populations.

A population of whole splenocytes cells were depleted of CD19 B cells, using anti- mouse CD19 positive selection (EasySep Stem Cell catalog#18754). Figure 18A illustrates that the remaining population was found to contain less than 10% B-cells (termed "B"). Figure 18B illustrates that knock-out B^" APCs stimulated T-cells less efficiently than wild type B^" APC. TPN decreased the S.I of wild type B^" APC, but did not change girk4 knock-out B^" APC activity.

EXAMPLE 10 - IL-12 production.

Interleukin 12 (IL-12) is naturally produced by dendritic cells and macrophages in response to antigenic stimulation. Therefore, the secretion of IL-12 from stimulated wild type and knock-out APCs was tested by ELISA. Figure 19 illustrates that knock-out APCs secrete lower levels of IL-12 as compared to wild type APC. This result supports the conclusion that APC originated from knock-out mice are antigen presenting defected. Pre-incubation with TPN did not influence IL-12 secretion. The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without undue experimentation and without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The means, materials, and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention.

Claims

1. A pharmaceutical composition comprising at least one G protein gated Inward Rectifying K+ channel 4 (GIRK4) inhibitor for use in treating an immune disorder.

2. The pharmaceutical composition of claim 1, wherein said GIRK4 inhibitor inhibits GIRK4 activity in lymphocytes.

3. The pharmaceutical composition of claim 2, wherein said GIRK4 inhibitor is capable of at least one activity selected from:

i. reducing the overall expression of GIRK4,

ii. neutralizing the functionality of GIRK4,

iii. inducing GIRK4 degradation, or

iv. any combination of (i)-(iii).

4. The pharmaceutical composition of claim 2, wherein said lymphocytes are selected from the group consisting of T cells and B cells.

5. The pharmaceutical composition of claim 4, wherein said B cells are selected from the group consisting of B-la cells, B-lb cells and B-2 cells.

6. The pharmaceutical composition of claim 5, wherein said B cells are B-la cells.

7. The pharmaceutical composition of claim 1, wherein said GIRK4 inhibitor is an antibody or an antigen-binding fragment thereof, capable of binding to GIRK4.

8. The pharmaceutical composition of claim 1, wherein said GIRK4 inhibitor is selected from the group consisting of Tertiapin, Charybdotoxin, Bupivacaine, Ethosuximide,

SCH23390 and U50488H.

9. The pharmaceutical composition of claim 8, wherein said GIRK4 inhibitor is Tertiapin.

10. The pharmaceutical composition of claim 1, wherein said immune disorder is selected from the group consisting of an autoimmune disease, an inflammatory disease, and an autoinflammatory disease.

11. The pharmaceutical composition of claim 10, wherein said autoimmune disease is multiple sclerosis (MS).

12. A method of treating an immune disorder in a subject in need thereof, comprising the step of administering to said subject a therapeutically effective amount of at least one G protein gated Inward Rectifying K+ channel 4 (GIRK4) inhibitor, thereby treating said immune disorder.

13. The method of claim 12, wherein said GIRK4 inhibitor inhibits GIRK4 activity in lymphocytes.

14. The method of claim 13, wherein said GIRK4 inhibitor is capable of at least one activity selected from:

i. reducing the overall expression of GIRK4,

ii. neutralizing the functionality of GIRK4,

iii. inducing GIRK4 degradation, or

iv. any combination of (i)-(iii).

15. The method of claim 13, wherein said lymphocytes are selected from the group consisting of T cells and B cells.

16. The method of claim 15, wherein said B cells are selected from the group consisting of B-la cells, B-lb cells and B-2 cells.

17. The method of claim 16, wherein said B cells are B-la cells.

18. The method of claim 12, wherein said GIRK4 inhibitor is an antibody or an antigen- binding fragment thereof, capable of binding to GIRK4.

19. The method of claim 12, wherein said GIRK4 inhibitor is selected from the group consisting of Tertiapin, Charybdotoxin, Bupivacaine, Ethosuximide, SCH23390 and U50488H.

20. The method of claim 19, wherein said GIRK4 inhibitor is Tertiapin.

21. The method of claim 12, wherein said immune disorder is selected from the group consisting of an autoimmune disease, an inflammatory disease, and an autoinflammatory disease.

22. The method of claim 21, wherein said autoimmune disease is multiple sclerosis (MS).

23. The method of claim 12, wherein said subject is a human.

24. A method for identifying a B cell as a regulatory B cell or as a B- la cell, comprising the step of detecting the presence of a GIRK protein in the membrane of said B cell.

25. The method according to claim 24, wherein said GIRK protein is detected with an antibody or an antigen-binding fragment thereof, an aptamer, or an inhibitor that specifically binds to said GIRK protein.

26. The method of claim 24, wherein said GIRK protein is selected from the group consisting of a GIRK1 protein, a GIRK2 protein, a GIRK3 protein and a GIRK4 protein.

27. The method of claim 26, wherein said GIRK protein is a GIRK4 protein.

28. The method of claim 24, further comprising the step of detecting IL-10 secretion from said B cell following stimulation of said B cell with an agent that elicits an immune response.

29. The method of claim 24, wherein said B cell is present in a biological sample.

30. The method of claim 29, wherein said biological sample is a liquid sample or a solid tissue sample.

31. The method of claim 30, wherein said liquid sample is a blood sample or a liquid sample obtained from a body cavity.

32. The method of claim 31 , wherein the body cavity is the peritoneal cavity or the pleural cavity.

33. The method of claim 30, wherein said solid tissue sample is derived from an immune organ selected from the group consisting of lymph node, spleen, bone marrow, Peyer's patch, tonsil and adenoid.

34. A method for identifying a B cell as a regulatory B cell or as a B- la cell, comprising the step of detecting the presence of an RNA molecule encoding a GIRK protein in said B cell.

35. The method according to claim 34, wherein said RNA molecule is detected by a nucleic acid probe that specifically hybridizes to said RNA molecule.

36. The method according to claim 35, wherein said nucleic acid probe is a primer for amplifying said RNA molecule by a nucleic acid amplification method.

37. The method of claim 34, wherein said GIRK protein is selected from the group consisting of a GIRK1 protein, a GIRK2 protein, a GIRK3 protein and a GIRK4 protein.

38. The method of claim 37, wherein said GIRK protein is a GIRK4 protein.

39. The method of claim 34, further comprising the step of detecting IL-10 secretion from said B cell following stimulation of said B cell with an agent that elicits an immune response.

40. The method of claim 34, wherein said B cell is present in a biological sample.

41. The method of claim 40, wherein said biological sample is a liquid sample or a solid tissue sample

42. The method of claim 41, wherein said liquid sample is a blood sample or a liquid sample obtained from a body cavity.

43. The method of claim 42, wherein said body cavity is the peritoneal cavity or the pleural cavity.

44. The method of claim 41, wherein said solid tissue sample is derived from an immune organ selected from the group consisting of lymph node, spleen, bone marrow, Peyer's patch, tonsil and adenoid.

45. A kit for use in the treatment an immune disorder, comprising a pharmaceutical composition comprising at least one GIRK4 inhibitor and a carrier; and instruction for use of said pharmaceutical composition for the treatment of said immune disorder.

46. A kit for use in identifying a B-cell as a regulatory B cell or as a B-la cell, said kit comprising an agent capable of identifying the presence of a GIRK protein in the membrane of said B cell; and instruction for use.

47. A kit for use in identifying a B-cell as a regulatory B cell or as a B-la cell, said kit comprising an agent capable of identifying the presence of a RNA molecule encoding a GIRK protein in said B cell; and instruction for use.