JPS6259841A - Method and instrument for measuring immunoreaction using linearly polarized light - Google Patents

Abstract

PURPOSE:To efficiently measure a sample with high accuracy and reproducibility by projecting a linearly polarized radiation to an antigen-antibody reactive liquid contg. at least an antigen and antibody to the sample. CONSTITUTION:The light radiated from a light source 1 is condensed by a collimator lens 2 and is then projected via a polarizer 3 to a cell 4. The reactive liquid 5 is contained in the cell 4. The linearly polarized light is scattered by the fine particles in the liquid 5 and the polarization condition of the scattered light changes according to the flocculation condition of the fine particles. Namely, the fine particles which are not flocculated to each other are spherical and therefore, the scattered light by the fine particles is linearly polarized. On the other hand, the scattered light is elliptically polarized if the antigen-antibody reaction takes place and the fine particles are flocculated to each other. The scattered light is, therefore, condensed by the lens 6 and is made incident on a photodetector 8 via an analyzer 7 having the plane of polarization orthogonal with the plane of polarization of the polarizer 3, then the output thereof changes according to the flocculation condition of the fine particles in the liquid 5, i.e., the antigen-antibody reaction condition. The immunoreaction is thus measured by detecting the output change of the detector 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for measuring an immune reaction based on an antigen-antibody reaction using light scattered by fine particles.

[Conventional technology]

There are immunoassay methods that utilize specific selective reactions of immune reactions as a method for measuring trace components in living bodies such as immune substances, hormones, pharmaceuticals, and immunomodulators.They can be roughly divided into labeled immunoassays that use enzymes or radioactive isotopes as labeling substances. There are two well-known methods: and non-labeled immunoassay, which directly measures antigen-antibody complexes.

The former labeled immunoassay methods include radioimmunoassay (RIA) and enzyme immunoassay (EIA).

Fluorescence immunoassay (FIA) is well known, and although it is highly sensitive, there are various limitations such as handling of isotopes and waste disposal.Moreover, measurements require a long time and labeling reagents are expensive. Therefore, there are drawbacks such as high inspection costs.

The latter non-labeled immunoassay methods include immunoelectrophoresis, immunodiffusion, and precipitation, and although they are simple analytical methods, they are insufficient for precise measurements in terms of sensitivity, quantitative performance, and reproducibility. Regarding this type of immunoassay method, please refer to "Clinical Testing Methods Summary" (authored by Izumihara Kanai, edited by Masamitsu Kanai, Metal Publishing) and "Clinical Testing J.
Vol.

22, Floor 5 (197g), pages 471-487.

Also \r1mmunochemistry J, VO
l, 12. th4 (1975), No. 349-351
In reality, particles carrying antibodies or antigens on their surfaces are reacted with antigens or antibodies, and the average diffusion constant, which is an index of Brownian motion that remains in proportion to the size of aggregated particles, is determined by the scattered light of laser light. Disclosed is a method for quantitatively analyzing an antigen or antibody by determining from changes in the spectral width of the antigen or antibody. Although this analytical method has the advantage of not using labeled reagents,
Since a spectrometer is used to detect the broadening of the spectrum of incident light due to the Donpla effect caused by the Brownian motion of particles, the device is large and expensive, and errors occur when mechanically driving the spectrometer. This has the disadvantage that accuracy and reproducibility deteriorate. Furthermore, this method only calculates the average diffusion constant from the spectral width of light, and has the disadvantage that the amount of information is small.

[Problem that the invention seeks to solve]

As mentioned above, conventional immunoassay methods use expensive labeling reagents, resulting in high analysis running costs, troublesome liquid handling and processing, long processing times, and high costs. It requires a large spectrometer, has poor accuracy and reproducibility, and is difficult to obtain.
There was also a drawback that the amount of ii was small.

The purpose of the present invention is to measure the antigen-antibody reaction by utilizing the fact that when linearly polarized light is scattered by fine particles, the polarization state of the scattered light is closely related to the antigen-antibody reaction. By eliminating the above-mentioned conventional drawbacks, it is possible to efficiently measure sequential samples with high accuracy and reproducibility without using expensive labeling reagents or expensive large spectrometers. An object of the present invention is to provide an immune reaction measurement method that can shorten the measurement time, automate the antigen-antibody reaction measurement, and obtain a lot of useful information about the antigen-antibody reaction, and an apparatus for carrying out such a method. It is something.

[Means and effects for solving the problem] The immune reaction measuring method of the present invention projects linearly polarized radiation onto an antigen-antibody reaction solution containing at least an antigen and an antibody, and Scattered light by fine particles added to the reaction solution or scattered light generated by antigen-antibody reaction of fine particles immobilized with antibodies or antigens added to the reaction solution is passed through an analyzer having a polarization plane orthogonal to the polarization plane of the linearly polarized radiation. It is characterized by detecting the antigen and measuring the antigen-antibody reaction based on this detection output.

Furthermore, the present invention projects light onto a reaction solution containing at least an antigen and an antibody, and uses scattered light by microparticles generated by an antigen-antibody reaction or an antigen-antibody reaction of antibodies added to the reaction solution or microparticles on which an antigen is immobilized. An apparatus for detecting the generated scattered light and measuring an antigen-antibody reaction based on the power spectral density of the intensity fluctuation of this detection output, which comprises a cell containing the antigen-antibody reaction solution and a cell for transmitting linearly polarized light to the cell. a light source device that makes the light incident on the cell; a photodetector device that receives the scattered light from the cell via an analyzer having a polarization plane perpendicular to the polarization plane of the linearly polarized light; and an output from the photodetector device. The method is characterized by comprising a means for receiving a signal, determining the power spectrum density of the intensity fluctuation, and measuring an antigen-antibody reaction based on the power spectrum density.

FIG. 1A is a conceptual diagram showing the basic configuration of the immune reaction measuring method according to the present invention. After the light emitted from the light source 1 is focused by the collimator lens 2, it passes through the polarizer 3 and is sent to the cell 4.
to project. The cell 4 contains a reaction liquid 5 in which a sample is mixed with colloidal fine particles on the surface of which an antibody or antigen that specifically causes an antigen-antibody reaction with the antigen or antibody to be measured in the sample is co-phased. The linearly polarized light is scattered by the particles in the reaction solution 5, and the polarization state of the scattered light changes depending on the state of aggregation of the particles. Since fine particles that are not aggregated with each other are spherical, they are polarized in the same direction as the vibration direction of the electric field vector of the electromagnetic wave of linearly polarized incident light. Therefore, the light scattered by the fine particles becomes linearly polarized light as it is. On the other hand, when an antigen-antibody reaction occurs and the fine particles aggregate with each other, the particle agglomerates no longer have a spherical shape, so they exhibit optical anisotropy, and the scattered light becomes elliptically polarized light. Therefore, when the scattered light is collected by the lens 6G and then incident on the photodetector 8 through the analyzer 7, which has a polarization plane perpendicular to the polarization plane of the polarizer 3, the output is determined by the particles of fine particles in the reaction liquid 5. It changes depending on the state of aggregation, that is, the state of antigen-antibody reaction. That is, if no aggregation occurs, the scattered light does not pass through the analyzer 7, but if aggregation occurs, the scattered light passes through the analyzer 7. Therefore, by detecting changes in the output of the photodetector 8, the immune reaction can be measured.

On the other hand, since the fine particles in the reaction solution move randomly due to Brownian motion, the output intensity of the photodetector fluctuates, and the power spectral density of this intensity fluctuation is the curve shown in Figure 1B if the fine particles are not aggregated. It becomes flat as shown by A. Such a power spectral density is generally called white. On the other hand, when fine particles aggregate, translational and rotational movements occur depending on their size and shape, and the power spectrum density of intensity fluctuation changes from white as shown by curve B. This change is in response to the antigen-antibody reaction. In other words, the power spectral density of the intensity fluctuation of the scattered light due to the movement of the aggregated fine particles by Brownian motion within the scattering volume and the intensity fluctuation of the scattered light due to the rotational movement of the particles deviates from white and increases.

In this way, the immune reaction can be measured by detecting the change in the power spectrum density of the scattered light intensity due to the fluctuation of the particles.

In the immune reaction measurement method of the present invention described above, antigen-
We focused on the fact that when linearly polarized light is incident on microparticles produced as a result of an antibody reaction or on which antibodies or antigens are immobilized, the polarization state of the scattered light depends on the shape and size of the microparticles. By detecting light through an analyzer with a polarization plane perpendicular to the polarization plane of the incident light, it is possible to determine whether there is an antigen-antibody reaction, quantify the antigen or antibody, and determine the aggregation state (particle size distribution) of microparticles due to the antigen-antibody reaction. You can get a lot of useful information. In this way, in the present invention, the scattered light is received by a photodetector and changes in the output signal are detected, so there is no need to use expensive labeling reagents and there is no need to perform spectrum analysis of the scattered light. There is no need to use a large and expensive spectrometer, and a lot of useful data regarding antigen-antibody reactions can be obtained in a short time with high sensitivity and high reproducibility.

[Example] FIG. 2 is a diagram showing the configuration of an example of the immune reaction measuring device according to the present invention. In this example, the light source that emits coherent light is t(e-N
An e-gas laser 11 is provided. - In addition to such a gas laser, a solid state laser such as a semiconductor laser can also be used as a light source that emits coherent light. light source 1
A laser beam 12 emitted from the laser beam 1 is separated into a beam 14 and a beam 15 by a semi-transparent mirror 13. One of the light beams 14 is condensed by a condenser lens 16, and then passed through a polarizer 17 made of, for example, a Glan-Thompson prism, and projected onto a transparent cell 18 as linearly polarized light. The other light beam 15 is made incident on a photodetector 19 made of a silicon photodiode and converted into a monitor signal representing fluctuations in the output light intensity of the light a11.

Inside the cell 18, there are spherical microparticles with antibodies or antigens bound to their surfaces, such as immunoglobulin G (IgG) on their surfaces.
) is housed in the antigen-antibody reaction solution 20, which is a mixture of a buffer solution in which polystyrene latex particles immobilized with polystyrene particles are dispersed, and a test solution containing an antigen or an antibody. Therefore cell 1
When an antigen-antibody reaction occurs in 8 and interaction occurs between the particles, the particles adhere to each other, which changes the polarization state of the scattered light and changes the state of Brownian motion. Scattered light scattered by the particles in the cell 18 is made incident on a collimator 21 having a pair of pinholes, passes through an analyzer 22 having a plane of polarization perpendicular to the plane of polarization of the polarizer 17, and then passes through an analyzer 22 consisting of a photomultiplier tube. Photodetector 2
3. The output monitor signal of the photodetector 19 is supplied to a data processing device 25 via a low noise amplifier 24.

Further, the output signal of the photodetector 23 is supplied to the data processing device 25 via a low noise amplifier 26 and a low pass filter 27. The data processing device 25 includes an A/D conversion section 28. A fast Fourier transform section 29 and an arithmetic processing section 30 are provided to perform signal processing as described later and output measurement results of antigen-antibody reactions. This measurement result is supplied to the display device 31 and displayed.

A lens and a mirror are provided between the analyzer 22 and the photodetector 23.

If an optical element such as a prism is placed, the light transmitted through the analyzer will be further affected, which may lead to measurement errors. Therefore, the output of the analyzer 22 is made to directly enter the photodetector 23. Moreover, if there is a scratch or the like on the cell 1, the polarization state will change, which is not preferable.

A reaction solution 20 containing spherical fine particles with antibodies or antigens immobilized on the surface is housed in the cell 18. When a linearly polarized light flux is incident on such a cell 18, the polarization of the scattered light is The state will change depending on the state of the particle. That is, when an antigen-antibody reaction is not performed and the particles do not aggregate, the optical isotropy of the spherical particles is not lost and the scattered light remains linearly polarized.

Therefore, the scattered light does not pass through the analyzer 22 and is detected by the photodetector 2.
The output of 3 is theoretically zero. In contrast, when an antigen-antibody reaction occurs and the particles aggregate, the particle agglomerate does not become spherical.
The light exhibits optical anisotropy, and thus the scattered light becomes elliptically polarized light, a portion of the scattered light passes through the analyzer 22, and the output of the photodetector 23 is no longer zero. In this case, a significant relationship is observed between the state of particle aggregation and the scattered light transmitted through the analyzer 22, and from this it is possible to detect the presence or absence of aggregation and the degree of aggregation.

The immune reaction measurement method of the present invention described above is in principle a zero method, and when the particles exist as a single substance without aggregation, there is no scattered light passing through the analyzer 22, so it is possible to measure the immune reaction with extremely high sensitivity. can be measured. That is,
If there is any output, it can be determined that an antigen-antibody reaction has occurred, and by using linearly polarized light, extremely sensitive measurements can be performed. Furthermore, since the polarization state of the scattered light depends on the degree of aggregation, the antigen in the sample can be quantified, for example, by determining the average value of the output of the photodetector 23. Furthermore, the aggregated particles undergo Brownian motion or rotation within the scattering volume, which causes the intensity of the scattered light to fluctuate. You can know the extent.

FIG. 3 is a diagram showing a detailed configuration of the collimator 21 shown in FIG. 2. The collimator 21 of this example has a hollow structure, and the hollow 21a has a dark box structure to eliminate the influence of external light, and its inner surface has an antireflection structure. Pinholes 21b and 21c are provided before and after the cavity 21a.
form. Now, these pinholes 21b and 21C
The radius of is a, and a2+the distance between the pinholes, respectively.

When the refractive index of the internal medium of the cavity 21a is n and the wavelength is λ, it is configured to satisfy the following formula (1).

λ In an embodiment of the present invention, the power spectral density of the intensity fluctuation of the scattered light is detected, and this power spectral density includes a term due to the fluctuation of the interference component due to the diffusion of the fine particles over a distance of about the wavelength, It consists of a term due to fluctuations in the number of particles caused by the movement of particles into and out of the scattering volume. Of these, fluctuations in scattered light due to interference are observed as spatial fluctuations in the speckle pattern, but if this is directly incident on the photodetector 26, which has a wide light-receiving surface, the light will be scattered spatially over the area of the light-receiving surface. As smoothing is performed, the detected fluctuation becomes smaller. Therefore, by limiting the field of view of the photodetector 23 using the collimator 21 having a pinhole as described above, fluctuations can be detected with high sensitivity. In this embodiment, in order to satisfy the above formula (1), it is practical enough to use air with a refractive index n=1 as the medium in the cavity 21a. In other words, the pinholes 21b and 21C with a diameter of 0.3 are 30c+
If the collimators 21 are separated by n, the above formula (1) will be satisfied.

In the embodiment described above, the light beam 14 incident on the self
and the optical axis direction of the collimator 21 are set at 90°,
Although the homodyne method in which the incident light flux does not directly enter the photodetector 23 is adopted, a heterodyne method in which a part of the incident light flux is made to enter the photodetector 23 may also be adopted. That is, in the present invention, as shown in FIG. 4, the angle θ between the light beam 14 incident on the cell 18 and the optical axis of the collimator 21 can be set arbitrarily. When detecting scattered light in a homodyne manner, a photodetector 2 consisting of a photomultiplier tube is used.
The output signal of No. 3 is proportional to the average value M of the square of the electric field strength of the scattered light Es, and in the case of heterogain detection in which the scattered light and the incident light are detected together,
If the electric field strength of the directly incident light is Ee, the photodetector 23
The output signal of is (Ee+Es)”=J +2Be −Es ÷W.Here, Ee has no fluctuation (even if there is, it is made loose compared to the fluctuation of the scattered light), so the photodetector The fluctuation component of the output of 23 is almost equal to the second term Ee -Es.In other words, an output signal that is approximately proportional to the electric field strength Es of the scattered light is obtained.

Further, the collimator 21 is not limited to the above-mentioned configuration, and may have any configuration as long as it can limit the field of view of the photodetector 23 to one speckle pattern or less.

Using the above-mentioned device, the output signal of the photodetector 23 is supplied to the data processing device 25 via the low-pass filter 27, and processed together with the monitor signal from the photodetector 19 to obtain the power spectrum of the intensity fluctuation of the scattered light. The results of determining the density will be explained below. Here, the power spectral density S (f) of steady state establishment process x (t) is calculated using fast Fourier transform based on this equation (2). That is, the output signal from the photodetector 23 is transmitted to the low noise amplifier 2.
6, the quantization level of the A/D conversion in the data processing device 25 is amplified so that the signal range is as wide as possible, and the quantized data is arithmetic processed by the microprocessor to obtain the power spectral density. The progress status of the immune reaction was numerically displayed on the display device 31 from the power vector density thus determined.

In Figure 5, the particle size is 0.2. About 1 latex particle of rJm
This shows the power spectrum density obtained when a liquid dispersed at a concentration of 0'1 particles/c+j is placed in the cell 18, and since the particles are almost completely separated, 1o31 (The power spectral density is approximately constant over the frequency of z.

As mentioned above, if the particles are completely spherical and completely separated, the output of the photodetector 23 will be zero, but in reality, the particles are not completely spherical and are completely separated. Since the output from the photodetector 23 is not zero, the output from the photodetector 23 is not zero. However, the power spectral density shows a nearly constant value.

Figure 6 shows the power spectral density when an antibody-antigen reaction occurs and particles aggregate. In this case, the power spectral density is not flat, but increases especially on the low frequency side. . This is because the power spectral density increases especially on the low frequency side due to the intensity fluctuation of the scattered light due to the movement of the aggregated particle mass within the scattering volume by Brownian motion, and the intensity fluctuation of the scattered light due to the rotational movement of the particle mass. be.

Figure 7 shows the power spectral density (curve A) of antibodies immobilized on the surface of polystyrene latex particles with a particle size of 0.2 μm before dispersion in a sample containing an antigen at a concentration of 4 x 10-9 g/ml and the power spectral density for 60 minutes. It shows the power spectrum density (curve B) after the reaction. The reason why the power spectral density is not flat even before the reaction is thought to be that some of the particles are aggregated by antibodies fixed on their surfaces. . On the other hand, the power spectral density after reacting for 60 minutes increases in the frequency range of approximately 10 to 102 Hz. Therefore, by comparing these curves, it is possible to detect whether an antigen-antibody reaction has occurred.

Figure 8 shows the change in power spectral density when antibodies are immobilized on the surface of polystyrene latex particles with a particle size of 0.2 μm and dispersed in a sample containing 8 x 10'' g/ml of antigen. This shows that.

Curves A to D show the power spectral densities before the reaction, 10 minutes, 30 minutes, and 60 minutes after the reaction, respectively. As is clear from these curves, as the immune reaction progresses and particle aggregation occurs, the power spectral density increases.

As mentioned above, the power spectral density changes depending on the aggregation of particles, but there are specific methods to detect whether an antigen-antibody reaction has occurred or to fix the antigen concentration from changes in the power spectral density. can be considered in various ways,
Some methods will be explained below.

The first method is to determine the relative fluctuation ratio of intensity fluctuations and determine the antigen concentration from the value of this ratio. As shown in FIG. 9, for the spectral density curve A before the reaction, the frequency f,
An integral value Sa from .

Then, the ratio R for the sample is determined, and from this the unknown antigen concentration in the sample can be determined.

The second method also determines the relative ratio of intensity fluctuations and determines the antigen concentration from the value of this ratio, but in this second method, the specific frequency f shown in FIG.

Power spectral densities 1a and I before and after the reaction in
This is a method of finding each b and then finding their ratio b R2=□. In this case, a also calculates R2 in advance for a sample with a known antigen concentration,
The concentration of the unknown antigen can be determined from the value of the ratio R2 determined for a sample with unknown antigen concentration.

The third method is to determine the frequencies f8 and fb of the rising portions of the power spectral density curves A and B before and after the reaction, as shown in FIG. 10, and to determine the antigen concentration from these frequencies. In this case, for example, the ratio R3-- of the frequencies f1 and f of the rising portion can be determined, and the antigen concentration can be determined from the fl value of this ratio.

The present invention is not limited to the embodiments described above, but can be modified and changed in many ways.

Although the above description has been exemplified with respect to immunoglobulin G (IgG), immunoglobulin A (IgA).

It can be applied to the measurement of all substances that cause agglutination due to antigen-antibody reactions, such as IgM, TgD, IgE, Australian antigen, syphilis antigen, and insulin.

Furthermore, in the above-mentioned example, antibodies were immobilized on the surface of microparticles to detect antigens in the specimen, but it is also possible to immobilize antigens on the surface of microparticles and detect antibodies in the specimen. can. Furthermore, although polystyrene latex particles were used as the fine particles in the above-mentioned examples, other organic particles,
Inorganic particles such as glass can also be used. Furthermore, in the above-mentioned examples, fine particles were present in the antigen-antibody reaction solution from the beginning, but without using such fine particles,
Scattered light from particulate products resulting from antigen-antibody reactions can also be used. An example of such an antigen-antibody reaction is a reaction using human chorionic gonadotropin (HCG) as an antigen and anti-human chorionic gonadotropin (anti-HCG) as an antibody, and the antigen-antibody complex generated by this reaction is The body can be treated as a particle. Furthermore, the antigen itself can also be used as particles. In such an antigen-antibody reaction, Candida albicans (yeast) is used as the antigen, and anti-Candida albicans is used as the antibody. In addition, blood cells, cells, microorganisms, etc. can also be used as particles.

Furthermore, in the example shown in Fig. 1, a hatch type was used in which the antigen-antibody reaction solution was stored in a cell and the measurement was performed, but a flow type in which the measurement was performed while the antigen-antibody reaction solution was continuously flowing may also be used. Of course it is possible.

Further, in the above embodiments, a laser light source that emits coherent light is used as the antigen, but a light source that emits incoherent light may also be used.

〔Effect of the invention〕

The effects of the present invention described above are summarized as follows.

(1) Since there is no need to use expensive and difficult-to-handle reagents such as labeling reagents such as enzymes and radioisotopes, it can be carried out at low cost and easily.

(2) It has higher precision and reproducibility than non-labeled immunoanalytical methods such as immunoelectrophoresis, immunodiffusion, and precipitation, so highly reliable measurement results can be obtained with high precision.

(3) Since linearly polarized light is used, it is in principle a zero method, and the photosensitivity can be detected. Therefore, highly accurate measurement can be performed with an ultra-trace amount of analyte, and the measurement time is short.

(4) Compared to the method of quantifying antigens or antibodies by determining the average diffusion constant from changes in the spectral width of scattered light, a spectrometer is not required, so the device is smaller and cheaper, and the measurement results are highly accurate and reliable. is obtained.

(5) When measurements are performed based on the power spectral density of optical fluctuations, a lot of useful information about antigen-antibody reactions can be obtained.

[Brief explanation of the drawing]

FIGS. 1a and 1b are conceptual diagrams showing the basic configuration and operation of the immune reaction measuring method according to the present invention, and FIG. 2 is a diagram showing the configuration of essential parts of an embodiment of the immune reaction measuring device of the present invention. FIG. 3 is a diagram showing the detailed configuration of the collimator,
FIG. 4 is a diagram showing the configuration of another embodiment of the immune reaction measuring device of the present invention, FIG. Figures 7 and 8 are graphs showing the power spectrum density of scattered light intensity fluctuations from aggregated fine particles.
The figure is a graph showing the power spectral density before and after the antigen-antibody reaction, and FIGS. 9 and 10 are graphs for explaining the method of measuring the antigen concentration from the power spectral density. ■...Light source, 2...Lens, 3...Polarizer, 4...
...Cell, 5...Reaction liquid, 6...Lens, 7...
Analyzer, 8... Photodetector, 11... Laser light source, 1
7... Polarizer, 18... Cell, 20... Reaction liquid,
2nd piece... Collimator, 22... Analyzer, 23...
Photodetector, 25...Data processing device, 26...Low noise amplifier, 27...Low pass filter, 28...A
/D converter, 29...Fast Fourier transform unit, 30...
- Arithmetic processing unit, 31... display device. Agent Patent Attorney Yusuke Hiraki Figure 1 Frequency (Hz) 7 Figure 5 6 Figure 6; Figure 7 Circular frequency ()-1z) Figure 8

Claims (1)

[Claims] 1. Projecting linearly polarized radiation onto a reaction solution containing at least an antigen and an antibody, and fixing light scattered by fine particles generated by an antigen-antibody reaction or the antibody or antigen added to the reaction solution. The scattered light generated by the antigen-antibody reaction of the microparticles is detected through an analyzer having a polarization plane perpendicular to the polarization plane of the radiation, and the antigen-antibody reaction is measured based on this detection output. Characteristic method for measuring immune reactions. 2. The immune reaction measuring method according to claim 1, wherein the antigen-antibody reaction is measured based on the power spectrum density of the intensity fluctuation of the detection output due to the antigen-antibody. 3. Light is projected onto a reaction solution containing at least an antigen and an antibody, and scattered light is generated by microparticles generated by an antigen-antibody reaction or scattered light caused by an antigen-antibody reaction of antibodies added to the reaction solution or microparticles on which an antigen is immobilized. A device that detects an antigen-antibody reaction and measures an antigen-antibody reaction based on the power spectrum density of the intensity fluctuation of the detection output, which comprises: a cell containing a reaction solution for performing the antigen-antibody reaction; and a cell that stores linearly polarized light into the cell. a light source device that makes the light incident on the cell; a photodetector device that receives the scattered light from the cell via an analyzer having a polarization plane perpendicular to the polarization plane of the linearly polarized light; and an output from the photodetector device. 1. An immune reaction measuring device using linearly polarized light, comprising means for receiving a signal, determining the power spectrum density of the intensity fluctuation, and measuring an antigen-antibody reaction based on the power spectrum density.