KR20180036310A - Method for Removing Leukocyte from Collected Blood - Google Patents

Abstract

Disclosed is a method for removing leukocytes from blood, capable of preventing deterioration of filtration performance due to long-term storage of blood. To this end, the method of the present invention comprises the following steps: selecting a blood filter based on a storage period after the collection of the blood; and removing leukocytes from the blood using the selected blood filter.

Description

Methods for Removing Leukocytes from Blood Collected from Blood [

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing leukocytes from a blood sample, and more particularly, to a method for removing leukocytes from blood by using an optimal blood filter selected based on a blood storage period, And a method for preventing performance degradation.

When blood or red blood cell concentrates containing white blood cells are transfused, side effects such as headache, vomiting, chills, fever, virus infection, and allogeneic antigen sensitization may occur. In order to prevent such side effects, it is necessary to remove the white blood cells present in the blood to be transfused before transfusion.

Among the methods for removing leukocytes from the blood include a centrifugal separation method in which white blood cells are separated by rotating the blood at a high speed, a filter method in which leukocytes are adsorbed and separated by allowing the blood to pass through the filter, There is a method of text to inhale and remove the separated white blood cell layer. Among them, a filter method having excellent leukocyte separation performance, easy operation and low cost is widely used.

These blood filters must meet various requirements. First, the blood filter should be able to treat large volumes of blood in a short time to prevent the blood from clotting. Second, the blood filter should have a high leukocyte removal rate to prevent the side effects mentioned above. Third, the blood filter must pass smoothly through the blood without damaging other useful components in the blood, such as red blood cells. Researches on blood filters that satisfy all three requirements have been actively conducted.

However, existing studies on leukocyte removal filters have focused only on the physical properties of the blood filter itself (ie, assuming all the blood have the same state) without considering the condition of the blood.

Accordingly, the present invention is directed to a method for removing leukocytes from blood, which can prevent problems due to limitations and disadvantages of the related art.

One aspect of the present invention is to provide a method for preventing leukocyte removal from blood by using an optimal blood filter selected based on a storage period of blood, thereby preventing deterioration of filtration performance due to long-term storage of blood.

Further features and advantages of the invention will be described hereinafter, and will in part be obvious from the description. Alternatively, other features and advantages of the invention may be learned through practice of the invention.

As one aspect of the present invention, there is provided a method of removing leukocytes from blood, comprising: selecting a blood filter based on a storage period after blood collection; And removing the leukocytes from the blood using the selected blood filter.

The blood filter may be selected from among first, second and third blood filters, each of the first, second and third blood filters comprising: a pre-processing filter for pre-processing the blood; And a main filter for treating the blood pretreated with the pretreatment filter, wherein the pretreatment filter is a laminate of first nonwoven fabrics having an average fiber diameter of 5 to 30 mu m and an average pore diameter of 10 to 30 mu m, Wherein the filter is a laminate of second nonwoven fabrics having an average fiber diameter of 1 to 5 占 퐉 and the second nonwoven fabric of the first blood filter has an average pore size of more than 5 占 퐉 and 7 占 퐉 or less, The nonwoven fabric has an average pore size of more than 7 mu m and less than 8 mu m, and the second nonwoven fabric of the third blood filter has an average pore diameter of more than 8 mu m and 10 mu m or less.

The first blood filter may be selected when the blood storage period is less than 24 hours and the second blood filter may be selected when the storage period after the blood collection exceeds 24 hours and less than 48 hours, The third blood filter may be selected when the storage period after blood collection is more than 48 hours but not more than 72 hours.

A second non-woven fabric of the first blood filter 28 g / m ² and may have a 30 g / m ² weight per unit area of less than, a second non-woven fabric of the second blood filter is 24 g / m ^2, greater than 28 g / m ² , and the second nonwoven fabric of the third blood filter may have a weight per unit area of not less than 20 g / m ^{2 and not more} than 24 g / m ² .

Each of the first and second nonwoven fabrics may include polyethylene terephthalate or polybutylene terephthalate.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed.

According to the present invention, since the leukocyte is removed from the blood using the optimal blood filter selected based on the storage period of the blood, the same blood filter is uniformly used even though the blood components are deformed according to the passage of time after the blood collection Can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a graph showing a pore size distribution of a second nonwoven fabric of a first blood filter (Example 1) according to an embodiment of the present invention,
1 is a graph showing a pore distribution of a second nonwoven fabric of a second blood filter (Example 2) according to an embodiment of the present invention,
1 is a graph showing a pore distribution of a second nonwoven fabric of a third blood filter (Example 3) according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the embodiments described below are provided for illustrative purposes only, and do not limit the scope of the present invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Therefore, the present invention encompasses all changes and modifications that come within the scope of the invention as defined in the appended claims and equivalents thereof.

In most countries, the performance of the blood filter is evaluated on the basis of constant blood. For example, in Korea, blood filters are evaluated based on blood having a blood storage time of less than 8 hours after blood collection, and in Europe, blood filters are evaluated based on blood having a blood storage time of less than 48 hours.

However, when blood transfusion is actually performed, stored blood for a longer period than the reference storage period is often used. When the blood is stored for a longer period of time, the shape and size of red blood cells are different. The erythrocytes present in the blood immediately after blood sampling are maintained in a discocyte form having a size of 2 to 4 탆, but they are transformed into a echinocyte form having a size of 7 to 8 탆 as the organ is preserved.

As described above, since the performance of the blood filter is evaluated based on the blood in a predetermined state in most countries, even if the blood filter passed the specific test, Performance often occurs.

According to the present invention, a blood filter is selected based on a storage period after blood collection, and white blood cells are removed from the blood using the selected blood filter.

According to an embodiment of the present invention, the blood filter may be selected from first, second and third blood filters.

Each of the first, second, and third blood filters includes a pre-processing filter for pre-processing the blood and a main filter for processing the blood pretreated by the pre-processing filter.

The pretreatment filter is a laminate of the first nonwoven fabrics and performs a pretreatment for removing macroaggregate due to aggregation of blood cells, which may occur during transport and storage of blood, from the blood flowing into the blood filter.

The main filter is a laminate of second nonwoven fabrics and removes white blood cells from the blood from which large particles have been removed by the pre-treatment filter.

The first and second nonwoven fabrics in which continuous or discontinuous fibers formed of polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) are entangled with each other to form a three-dimensional network structure can be produced by a meltblown method .

The fibers of the first and second nonwoven fabrics preferably each have a diameter variation coefficient of 30 CV% or less. The diameter variation coefficient is a percentage of the standard deviation with respect to the average fiber diameter. The diameter variation coefficient of 30 CV% or less can ensure a uniform blood flow throughout the first and second nonwoven fabrics, and as a result, excellent filtration efficiency and filtration performance can be constantly exhibited.

According to one embodiment of the present invention, the first nonwoven fabrics of the first, second and third blood filters have an average fiber diameter of 5 to 30 mu m and an average pore diameter of 10 to 30 mu m.

When the average fiber diameter of the first nonwoven fabric is less than 5 mu m, the strength of the fiber is weak and soft, so that the nonwoven fabric is squeezed by filtration due to the free fall of blood, the gap between adjacent fibers becomes narrow, Can be increased sharply. On the other hand, when the average fiber diameter of the first nonwoven fabric exceeds 30 탆, the surface area of the fiber filled for filtration decreases, and the chance of contact with the blood cells is reduced.

If the average pore diameter of the first nonwoven fabric is less than 10 mu m, large particles including leukocyte can not pass through the first nonwoven fabric, and blood cells are excessively collected in the first nonwoven fabric, shortening the filtration life. On the other hand, when the average pore size of the first nonwoven fabric exceeds 30 탆, large particles including leukocyte are not filtered by the pre-filter and reaches the main filter, so that the life of the second nonwoven fabric is shortened, Can be increased infinitely.

Wherein the first nonwoven fabric of the first, second and third blood filters comprises: melting polyethylene terephthalate or polybutylene terephthalate to prepare a first dope; placing the first dope in a first die ) To form a first fiber, and collecting the first fiber on a first collector. At this time, the distance from the first die to the first collector (DCD) may be 200 mm or more.

The first dope radiating step includes ejecting the first dope through a nozzle of the first die and injecting high temperature and pressure air into the second dope immediately before being ejected through the nozzle . At this time, the angle between the nozzle and the air may be 30 to 120 °. In order to uniformly adjust the average fiber diameter and the average pore diameter of the first nonwoven fabric, the angle between the nozzle and the air is preferably 45 to 60 ° Do.

Then, the pre-treatment filter can be obtained by stacking the first nonwoven fabrics so that the packing density of the pre-treatment filter with respect to the target blood throughput of the blood filter is 0.1 to 1 g / 100 ml, preferably 0.11 to 0.15 g / 100 ml .

When the filling density of the pretreatment filter is less than 0.1 g / 100 ml, large particles due to blood coagulation which may occur during transportation and storage of blood reach the main filter having a relatively small average pore passing through the pre- As a result, the flow of blood may be disturbed, which may significantly reduce the filtration rate and even cause clogging of the filter. On the other hand, when the packing density of the pretreatment filter exceeds 1 g / 100 ml, the case of the blood filter may be unnecessarily enlarged and the main filter may be excessively squeezed to reduce the average pore size. As a result, It may result in a falling problem.

According to one embodiment of the present invention, the second nonwoven fabric of the first, second and third blood filters has an average fiber diameter of 1 to 5 mu m.

If the average fiber diameter of the second nonwoven fabric constituting the main filter is less than 1 占 퐉, the pressure loss during filtration of the blood may be increased, and the weakness of the fibers may cause cutting of fibers and generation of fibers. The blood transfusion reaction may be caused by being included in the blood. On the other hand, when the average fiber diameter of the second nonwoven fabric exceeds 5 탆, the probability of the fibers contacting the leukocyte is lowered, so that the leukocyte removal rate of the second nonwoven fabric may be lowered.

The second nonwoven fabric of the first, second and third blood filters has a maximum pore size of 10 to 30 탆, preferably 10 to 15 탆, so that only the white blood cells can be selectively adsorbed and the red blood cells and platelets can be passed as they are.

According to an embodiment of the present invention, the second nonwoven fabric of the first blood filter has an average pore size of more than 5 μm and less than 7 μm, and the second nonwoven fabric of the second blood filter has an average pore diameter And the second nonwoven fabric of the third blood filter has an average pore size of more than 8 mu m and 10 mu m or less.

In the first to third blood filters, if the average pore size of the second nonwoven fabric is not more than the lower limit of the numerical value range, the red blood cells can not smoothly pass through the main filter, and the blood loss rate is significantly decreased due to the high pressure loss. Clogging may be induced. On the other hand, in the first to third blood filters, when the average pore size of the second nonwoven fabric exceeds the upper limit value of the numerical value range, leukocytes having a size of 12 to 25 탆 can easily pass through the main filter, The leukocyte removal rate may be lowered.

A second non-woven fabric of the first blood filter 28 g / m ² and may have a 30 g / m ² weight per unit area of less than, a second non-woven fabric of the second blood filter is 24 g / m ^2, greater than 28 g / m ² , and the second nonwoven fabric of the third blood filter may have a weight per unit area of not less than 20 g / m ^{2 and not more} than 24 g / m ² .

The second nonwoven fabric of the first blood filter may have an average thickness of 0.15 to 0.16 mm and the second nonwoven fabric of the second blood filter may have an average thickness of 0.14 to 0.15 mm, The second nonwoven fabric may have an average thickness of 0.13 to 0.14 mm.

Second nonwoven fabrics of the first, second and third blood filters are prepared by melting polyethylene terephthalate or polybutylene terephthalate to prepare a second dope, radiating the second dope through a second die, Forming a fiber, and collecting the second fiber on a second collector.

Wherein the second dope radiating step includes ejecting the second dope through a nozzle of the second die and injecting high temperature and pressure air into the second dope immediately prior to ejection through the nozzle .

The angle between the nozzle and the air may be set to 45 to 60 degrees. When the angle is less than 45 °, the angle of the nozzle becomes sharp, and damage due to the impact upon attachment and detachment of the nozzle becomes severe, so that it is difficult to mass-produce and control, and the radiated fibers are oriented only in one direction, And the filtration time is increased. On the other hand, when the angle exceeds 60 °, the fibers radiated from the nozzle and the air at high temperature and high pressure form turbulence, which causes serious problems in controlling the average pore diameter.

Generally, as the DCD increases, the moving distance of the air at high temperature and high pressure and the radiated fibers becomes longer, and the unevenness of the average pore diameter tends to increase due to decrease of the lamination uniformity of the fibers. Therefore, according to an embodiment of the present invention, the DCD applied to the first nonwoven fabric for the pre-treatment filter is 200 mm or more, while the DCD applied to the second nonwoven fabric for the main filter is preferably 60 mm or less.

The second dope discharge amount and / or the process speed (i.e., the winding speed of the second nonwoven fabric) are controlled within the range of 135 to 145 g / min and the range of 6 to 10 m / min, respectively, The weight per unit area can be adjusted. That is, the second nonwoven fabrics of the first, second and third blood filters of the present invention having different average pore sizes and different unit area weights can be produced by different conditions of at least one of the second dope discharge amount and the process speed . As the second dope discharge amount is smaller and the process speed is higher, the average pore diameter of the second nonwoven fabric increases and the weight per unit area decreases.

For example, the second non-woven fabric of the first blood filter can be produced by setting the process speed to 6 to 7 m / min while the second dope discharge amount is fixed at 140 g / min, 7 to 8 m / min to produce the second nonwoven fabric of the second blood filter, and the second nonwoven fabric of the third blood filter can be produced by setting the processing speed to 8 to 10 m / min.

Subsequently, the second nonwoven fabric is laminated so that the filling density of the main filter with respect to the target blood throughput of the blood filter is 1 to 3 g / 100 ml, thereby producing the main filter.

After the pretreatment filter and the main filter manufactured as described above are installed in the case, they are sealed using an ultrasonic welder to prevent blood leaking, and they are selectively sealed at a temperature of 100 to 120 ° C and a pressure of 1 to 1.2 kgf / cm ² for 20 minutes Second, and third blood filters of the present invention can be obtained by performing sterilization treatment for 1 hour to 1 hour.

According to an embodiment of the present invention, if the first blood filter is selected when the blood to be filtered is stored for a period of not more than 24 hours after the blood collection, and the storage period after the blood collection exceeds 24 hours and less than 48 hours, The blood filter is selected and the third blood filter is selected when the storage period after the blood collection is more than 48 hours but not more than 72 hours.

As described above, since the leukocyte is removed from the blood using the optimal blood filter selected based on the storage period of the blood, the same blood filter is uniformly used even though the blood components are deformed with time after the blood collection, Thereby avoiding problems that may occur.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. It should be noted, however, that the following examples are intended to assist the understanding of the present invention and should not limit the scope of the present invention thereby.

Experimental Example 1: Measurement of average fiber diameter (占 퐉) of nonwoven fabric

The average fiber diameter of the nonwoven fabric was determined using a scanning electron microscope and an image analyzer (JVC Digital Camera KY-F70B was used in Image-Pro Plus software). The average fiber diameter of 20 samples was measured and the average value was calculated.

Experimental Example 2: Measurement of average pore diameter (占 퐉) of nonwoven fabric

The average pore size (탆) of the nonwoven fabric was measured using a Capillary Flow Porometer (PMI, CFL-1100-AE) according to the ASTM F 316-03 standard. Specifically, a circular specimen having a diameter of 1 inch was thoroughly wetted with a Galwick solution having a surface tension of 15.9 dyne / cm, and then put into the above equipment. The average pore size of 10 samples was measured and the average value was calculated.

Experimental Example 3: Measurement of average thickness (mm) of nonwoven fabric

Six points of equal spacing (100 mm) were selected in the width direction (CD direction) of the nonwoven fabric and the thickness of the nonwoven fabric at each point was measured by dial thickness gauge (Mitutoyo / 10 (0.01) mm) . The six points were selected in a state in which left and right side portions of 70 mm in the width direction of the nonwoven fabric were excluded.

Example 1

Polybutylene terephthalate having an intrinsic viscosity of 0.52 and a melting point of 224 캜 was melted at 250 캜 to prepare a spinning solution, and then, using a conventional meltblown nonwoven fabricating apparatus, the first nonwoven fabric for a pretreatment filter And a second nonwoven fabric for a main filter were respectively prepared.

Specifically, the dope discharge amount and the air temperature were adjusted under an air pressure of 0.7 kgf / cm ² and a DCD of 250 mm to adjust the average fiber diameter of 11 탆, the average pore diameter of 24.1 탆, the weight per unit area of 35 g / m ² , Of the average thickness of the first nonwoven fabric. Further, under an air pressure of 1.2 kgf / cm ² , an air temperature of 250 ° C, a DCD of 50 mm, an angle between the nozzle and air of 60 °, a dope discharge amount of 140 g / min and a process speed of 6.4 m / , An average pore diameter of 6.12 mu m, a weight per unit area of 28.5 g / m < ² > and an average thickness of 0.155 mm. 1 is a graph showing the pore distribution of the second nonwoven fabric.

The first and second nonwoven fabrics were then cut to a filtration area of 32 cm ² .

The cut nonwoven fabrics were laminated to prepare a 1.116 g pretreatment filter. The cut nonwoven fabrics were laminated to form a main filter of 5.412 g. The pretreatment filter and the main filter were mounted in a polycarbonate case, A blood filter having a target blood throughput of 330 ml was prepared by sealing with a fusion machine.

Then, the blood filter was completed by sterilizing the blood filter at a temperature of 115 ° C and a pressure of 1.15 kgf / cm ² for 30 minutes.

Example 2

Applying a process speed of 7.3 m / min in the production of the second nonwoven fabric, a second nonwoven fabric having an average pore size of 7.50 μm, a weight per unit area of 24.5 g / m ² and an average thickness of 0.145 mm was obtained The blood filter was completed in the same manner as in Example 1. 2 is a graph showing the pore distribution of the second nonwoven fabric.

Example 3

By applying a process speed of 8.7 m / min in the production of the second nonwoven fabric, a second nonwoven fabric having an average pore size of 8.83 탆, a weight per unit area of 21.3 g / m ² and an average thickness of 0.135 mm was obtained The blood filter was completed in the same manner as in Example 1. 3 is a graph showing the pore distribution of the second nonwoven fabric.

Comparative Example 1

Except that a second nonwoven fabric having an average pore size of 10.70 mu m, a weight per unit area of 16.3 g / m < ² > and an average thickness of 0.125 mm was obtained by applying a process speed of 10.1 m / min in the production of the second nonwoven fabric. The blood filter was completed in the same manner as in Example 1.

Comparative Example 2

By applying a process speed of 5.5 m / min in the production of the second nonwoven fabric, a second nonwoven fabric having an average pore size of 4.70 μm, a weight per unit area of 31.0 g / m ² and an average thickness of 0.17 mm was obtained The blood filter was completed in the same manner as in Example 1.

The filtration times, erythrocyte recovery rates, residual leukocyte count, and residual leukocyte counts of the blood filters obtained by the above-described Examples and Comparative Examples were measured for the first, second and third blood samples stored for 24 hours, 48 hours, and 72 hours, respectively, And filtration performance were obtained using the following methods, respectively.

* Filtration time (min)

The filtration time was from 310 to 350 ml of red blood cell preparation (average 330 ml) containing SAG-M (saline, adenine, glucose, mannitol: 88.9 ml) used as an additive to extend the blood shelf life The time taken for filtration was measured.

* Red blood cell recovery rate % )

A blood filter was installed on a stand having a height of 2 m, and blood was directly connected to a tube through which whole blood was passed. Then, 15 cc of blood before and after filtration was collected and analyzed using an automated hematology analyzer (SYSMEX, XP-300) , The amount of blood cells was quantitatively measured under the conditions shown in Table 1 below to obtain the red blood cell recovery rate.

division Auto CBC Reference RBC Counter 3.80 to 6.5 M / WBC Counter 4.0 to 11.0 K / WBC differential counter Lym-: 20-45%, Neutro-: 40-75% Hemoglobin (Hb) 11.5 to 18 g / dL Hematocrit (Hct) 37.0 to 50.0% Platelet 150 to 400 K / l

* After filtration, residual leukocyte (1 × 10 ⁶ / unit)

Leucocyte count was measured using LeucoCOUNT Kit, one of the bead-based flow cytometry methods. 100 μl of blood was added to a TruCOUNT tube containing a predetermined number of beads, and then 400 μl of a LeucoCOUNT reagent containing RNAse, detergent and propidium iodidePI) was added to the TruCOUNT tube and allowed to react in a dark room for 5 minutes. After counting the number of beads (R1) and number of leukocytes (R2) using FACS (BD bioscience, San Jose, CA, USA), residual leukocytes after filtration were calculated by the following Equation 2.

* Filtration performance

Considering all the factors measured by the above methods, the filtration performance of the blood filter was evaluated as grade 4 (?: Very good,?: Good,?: Normal, poor: poor).

The filtration time, erythrocyte recovery rate, residual leukocyte, and filtration performance of the blood filters measured by the above methods are shown in Table 2 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Second nonwoven fabric Average pore size (탆) 6.12 7.50 8.83 10.70 4.70 Weight per unit area
(g / m ² ) 28.5 24.5 21.3 16.3 31.0 Average thickness (mm) 0.155 0.145 0.135 0.125 0.17 First blood
(24 hr) Filtration time (min) 16.7 11.3 9.6 5.3 45.0 Red blood cell recovery (%) 91.7 92.1 90.9 93.5 80.3 Residual white blood cells
(1 x 10 < ⁶ > / unit) 0.03 0.36 0.81 3.34 0.03 Filtration performance ◎ Δ Δ × Δ Second blood
(48 hr) Filtration time (min) 30.4 15.5 12.7 7.9 60.0 Red blood cell recovery (%) 81.3 90.2 91.6 93.7 68.4 Residual white blood cells
(1 x 10 < ⁶ > / unit) 0.00 0.03 0.24 2.71 0.00 Filtration performance × ◎ Δ × × Third blood
(72 hr) Filtration time (min) 60.0 33.7 14.6 8.9 60.0 Red blood cell recovery (%) 72.8 87.8 89.4 93.1 53.9 Residual white blood cells
(1 x 10 < ⁶ > / unit) 0.00 0.04 0.07 2.60 0.00 Filtration performance × Δ ◎ × ×

Claims (5)

A method for removing leukocytes from blood,
Selecting a blood filter based on the storage period after the blood collection; And
And removing the leukocytes from the blood using the selected blood filter.
A method for removing white blood cells from blood. The method according to claim 1,
Wherein the blood filter is selected from first, second and third blood filters,
Wherein each of the first, second and third blood filters comprises:
A pretreatment filter for pretreating the blood; And
And a main filter for processing the blood pretreated by the pre-processing filter,
The pretreatment filter is a laminate of first nonwoven fabrics having an average fiber diameter of 5 to 30 mu m and an average pore diameter of 10 to 30 mu m,
The main filter is a laminate of second nonwoven fabrics having an average fiber diameter of 1 to 5 mu m,
The second nonwoven fabric of the first blood filter has an average pore size of more than 5 mu m and 7 mu m or less,
The second nonwoven fabric of the second blood filter has an average pore size of more than 7 mu m and less than 8 mu m,
Wherein the second nonwoven fabric of the third blood filter has an average pore size of more than 8 [mu] m but not more than 10 [
A method for removing white blood cells from blood. 3. The method of claim 2,
The first blood filter is selected when the blood storage period after the blood collection is 24 hours or less,
The second blood filter is selected when the storage period after blood collection is more than 24 hours but less than 48 hours,
Wherein the third blood filter is selected when the storage period after blood collection is more than 48 hours but not longer than 72 hours.
A method for removing white blood cells from blood. 3. The method of claim 2,
A second non-woven fabric of the first blood filter has a 28 g / m ² greater than 30 g / m basis weight of not more than ^2,
It said second blood filter has a second non-woven fabric 24 g / m ² greater than 28 g / m ² weight per unit area of less than a,
The third blood filter of the second non-woven fabric, characterized in that it has a 20 g / m ² greater than 24 g / m ² weight per unit area of less,
A method for removing white blood cells from blood. 3. The method of claim 2,
Characterized in that each of the first and second nonwoven fabrics comprises polyethylene terephthalate or polybutylene terephthalate.
A method for removing white blood cells from blood.

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