JPH0556817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides an immunological reaction based on an antigen-antibody reaction.
The present invention relates to a method and apparatus for measuring 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 oxygen or radioactive isotopes as labeling substances. There are two well-known methods: and a non-labeled immunoassay method that directly measures antigen-antibody complexes.

Radioimmunoassay (RIA), appeal immunoassay (EIA), and fluorescence immunoassay (FIA) are well known as the former labeled immunoassay, and although they are highly sensitive, they require handling of isotopes and waste disposal. There are various limitations such as these, and there are also drawbacks such as a long time required for measurement and high testing costs due to the expensive labeling reagents.

The latter non-labeled immunoassay method includes immunoelectrophoresis,
There are immunodiffusion methods, precipitation methods, etc., which are simple analytical methods, but are insufficient for precise measurements in terms of sensitivity, quantitative performance, and reproducibility. Regarding this type of immunoassay method, please refer to "Clinical Testing Method Summary" (authored by Izumihara Kanai, edited by Masamitsu Kanai, published by Kanehara Publishing) and "Clinical Testing" Vol. 22, No. 5.
(1978), pp. 471-487.

Also, "Immunochemistry", Vol.12, No.4
(1975), pp. 349-351, in which particles carrying antibodies or antigens on their surfaces are reacted with antigens or antibodies, the average diffusion constant, which is an index of Brownian motion, decreases in proportion to the size of aggregated particles. Disclosed is a method for quantitatively analyzing an antigen or antibody by determining from changes in the spectral width of scattered laser light. Although this analysis method has the advantage of not using labeled reagents, it uses a spectrometer to detect the broadening of the spectrum of incident light due to the Doppler effect caused by the Brownian motion of particles, so the equipment is large and expensive. In addition, there is a drawback that errors occur when mechanically driving the spectrometer, resulting in poor accuracy and reproducibility. In addition, this method only calculates the average diffusion constant from the spectral width of light.
Another disadvantage is 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 handling and processing of liquids, and long processing times. The drawbacks are that it requires a large spectrometer, has poor accuracy and reproducibility, and provides only a small amount of information.

The object of the present invention is that when linearly polarized light is scattered by microparticles, the polarization state of the scattered light changes from antigen to antigen.
By measuring the antigen-antibody reaction by taking advantage of its close relationship with the antibody reaction, the above-mentioned conventional drawbacks can be removed, and without using expensive labeling reagents or expensive and large spectrometers. Sequential measurements can be carried out efficiently with high accuracy and reproducibility.
Furthermore, the present invention aims 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 implementing such a method. It is something to do.

[Means and actions for solving problems]

The immune reaction measurement method of the present invention projects linearly polarized radiation onto an antigen-antibody reaction solution containing at least an antigen and an antibody, and detects scattered light by fine particles generated by the antigen-antibody reaction or antibodies added to the reaction solution. Alternatively, the scattered light generated by the antigen-antibody reaction of microparticles on which the antigen is immobilized is detected through an analyzer having a polarization plane perpendicular to the polarization plane of the linearly polarized radiation, and based on this detection output, the - It is characterized by measuring an antibody reaction.

Furthermore, the present invention projects light onto a reaction solution containing at least an antigen and an antibody, and detects the scattered light by microparticles generated by an antigen-antibody reaction or the antigen-antibody reaction of an antibody added to the reaction solution or microparticles on which an antigen is immobilized. An apparatus for detecting the resulting scattered light and measuring an antigen-antibody reaction based on the power spectral density of the intensity fluctuation of the detection output, comprising: a cell containing the antigen-antibody reaction solution; and a cell containing the linearly polarized light. a light source device that makes the light incident on the cell; a photodetector device that receives scattered light from the cell via an analyzer having a polarization plane orthogonal to the polarization plane of the linearly polarized light; The device is characterized in that it receives the output signal of the device, determines the power spectrum density of the intensity fluctuation, and measures the 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,
The light is projected onto a cell 4 through a polarizer 3. The cell 4 contains a reaction liquid 5 in which a sample is mixed with colloidal particles having antibodies or antigens immobilized on the surface that cause specific antigen-antibody reactions with the light source or antibody to be measured in the sample. 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 particles becomes linearly polarized light, and the linearly polarized light becomes linearly polarized light. 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, after the scattered light is focused by the lens 6, when it is made incident on the photodetector 8 through the analyzer 7, which has a polarization plane perpendicular to the polarization plane of the polarizer 3, its output is reflected in the reaction liquid 5. It changes depending on the state of aggregation of the microparticles, that is, the state of the antigen-antibody reaction. That is, the scattered light does not pass through the analyzer 7 when no aggregation occurs, but the scattered light passes through the optical analyzer 7 when aggregation occurs. 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 spectrum density of this intensity fluctuation is as shown in Figure 1B if the fine particles are not aggregated.
The curve becomes flat as shown by curve 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. That is, the power spectral density of the intensity fluctuation of scattered light due to the movement of aggregated fine particles in the scattering volume by Brownian motion, and the intensity fluctuation of scattered light due to the rotational movement of 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, when linearly polarized light is incident on microparticles produced as a result of an antigen-antibody reaction or on microparticles on which antibodies or antigens are immobilized, the polarization state of the scattered light changes to that of the microparticles. By focusing on the fact that the antigen depends on the shape and size of the antigen, we detect the scattered light through an analyzer whose polarization plane is orthogonal to the polarization plane of the incident light.
Presence or absence of antibody reaction, quantification of antigen or antibody, antigen-
It is possible to obtain a lot of useful information such as the aggregation state (flow diameter distribution) of microparticles due to antibody reactions. 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 embodiment of the immune reaction measuring device according to the present invention. In this example,
Wavelength as a light source that emits coherent light
A 632.8 nm He-Ne gas laser 11 is provided. In addition to such a gas laser, a solid laser such as a semiconductor laser can also be used as a light source that emits coherent light. A laser beam 12 emitted from a light source 11 is converted into a beam 14 by a semi-transparent mirror 13.
and a luminous flux 15. 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 source 11.

Inside the cell 18, there is a buffer in which spherical fine particles having antibodies or antigens bound to their surfaces, such as polystyrene latex particles having immunoglobulin G (IgG) immobilized on their surfaces, are dispersed, and a sample containing the antigen or antibodies. Antigen-antibody reaction liquid 20, which is a mixture with
to accommodate. Therefore, when an antigen-antibody reaction occurs in the cell 18 and interaction occurs between particles,
Since the fine particles adhere to each other, the polarization state of the scattered light changes and the state of Brownian motion also changes. 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 a photomultiplier tube. The light is incident on a photodetector 23 consisting of: The output monitor signal of the photodetector 19 is sent to the low noise amplifier 24.
The data is supplied to the data processing device 25 via the. Further, the output signal of the photodetector 23 is passed through a low-noise amplifier 26 and a low-pass filter 27 to a data processing device 25.
supply to. The data processing device 25 is provided with an A/D conversion section 28, a fast Fourier transform section 29, and an arithmetic processing section 30, performs signal processing as described below, and outputs the measurement results of the antigen-antibody reaction. This measurement result is supplied to the display device 31 and displayed. If an optical element such as a lens, mirror, or prism is placed between the analyzer 22 and the photodetector 23, the light that has passed 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 18, 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,
If no antigen-antibody reaction occurs 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 transmitted through the photodetector 23.
The output of is theoretically zero. On the other hand, when an antigen-antibody reaction occurs and the particles aggregate, the particle agglomerate does not become spherical and exhibits optical anisotropy, so that the scattered light becomes elliptically polarized light, and a portion of the scattered light is detected. The photon 22 is now transmitted, and the photodetector 2
The output of 3 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 particles exist as a single substance without aggregation, there is no scattered light passing through the analyzer 22, so the immune reaction can be measured with extremely high sensitivity. can do. That is, if there is any output, it can be determined that an antigen-antibody reaction has occurred, and by using linearly polarized light, measurement can be performed with extremely high sensitivity. Further, since the polarization state of the scattered light depends on the degree of aggregation, the antigen in the sample can be quantified by determining the average value of the output of the photodetector 23, for example. Furthermore, the aggregated particles undergo Brownian motion or rotation within the scattering volume, which causes the intensity of the scattered light to fluctuate, and the degree of aggregation can be estimated by determining the power spectral density of this intensity fluctuation. You can know.

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 remove the influence of external light, and its inner surface has an antireflection structure. Pinholes 21b and 21c are formed before and after the cavity 21a.
Now, when the radius of these pinholes 21b and 21c are a ₁ and a ₂ respectively, the distance between the pinholes is L, the refractive index of the internal medium of the cavity 21a is n, and the wavelength is λ, the following equation (1) can be written. Configure to your satisfaction.

L≧4na ₁ a ₂ /λ ...(1) In one embodiment of the present invention, the power spectral density of the intensity fluctuation of scattered light is detected, but this power spectral density is determined by the fact that fine particles diffuse over a distance of approximately the wavelength. The term consists of a term due to the fluctuation of the interference component due to the movement of the particles, and a term due to the fluctuation of the number of particles caused by the movement of fine particles into and out of the scattering volume. Of these, fluctuations in the 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), the medium in the cavity 21a is air having a refractive index of n=1, which is sufficiently practical. In other words, the pinholes 21b and 21c with a diameter of 0.3mm are
If the collimators 21 are spaced apart by cm, the above equation (1) will be satisfied.

In the embodiment described above, the direction of the light beam 14 incident on the cell 7 and the optical axis direction of the collimator 21 are set at 90 degrees Celsius, and the homodyne method is adopted in which the incident light beam does not directly enter the photodetector 23. It is also possible to adopt a heterodyne method in which a part of the light is incident on the photodetector 23. 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, the output signal of the photodetector 23 consisting of a photomultiplier tube is based on the electric field intensity of the scattered light.
Let Es be proportional to the average value of its square, ² _s . In the case of heterodyne detection in which scattered light and incident light are detected together, if Ee is the electrolytic intensity of direct incident light, then photodetection The output signal of the device 23 is (+) ² =E ² _e +2Ee·÷ ² _s . Here, since Ee has no fluctuation (even if it does, it is made looser than the fluctuation of the scattered light), the fluctuation component of the output of the photodetector 23 is almost equal to the second term Ee. In other words, an output signal approximately proportional to the electric field strength of the scattered light can be 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 passed through the low-pass filter 27 to the data processing device 2.
5 and processed together with the monitor signal from the photodetector 19 to obtain the power spectrum density of the intensity fluctuation of the scattered light. The results will be described below. Here, the power spectral density S(t) of the steady-state establishment process ×(t) is
It can be expressed as follows.

s(t)＝ ^lim _T → _∞ 1/2T＜｜∫ ^T _-T x(t)e ^-2ift dt｜ ² ＞…
...(2) Based on this equation (2), the power spectral density is calculated using fast Fourier transform. That is,
The output signal from the photodetector 23 is transmitted to a low noise amplifier 26.
The quantization level of the A/D conversion in the data processing device 25 is amplified so as to cover the signal range as wide as possible, and the quantized data is 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 spectral density thus determined.

Figure 5 shows the number of latex particles with a particle size of 0.2 μm.
This shows the power spectrum density obtained when a liquid containing particles dispersed at a concentration of 10 ¹¹ particles/cm ³ is placed in the cell 18. Since the particles are almost completely separated, 10 ^-1 ~ The power spectral density remains approximately constant over the frequency of 10 ³ Hz.

As mentioned above, if the particles are completely spherical and completely separated, the photodetector 23
The output of the photodetector 23 is zero, but in reality the particles are not completely spherical and are not completely separated, so the output of 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 anti-body-antigen reaction occurs and particles aggregate. In this case, the power spectral density is not flat and sometimes increases on the low frequency side. Become. 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. It's for a reason.

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 being dispersed into a sample containing antigen at a concentration of 4 × 10 ^-9 g/ml. It shows the power spectrum density (curve B) after reacting for 60 minutes. 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 60 minutes of reaction increases in the frequency range of approximately 10 ^-1 to 10 ² 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 antigen at a concentration of 8 x 10 ^-8 g/ml. It is something. Curve A
~D are before reaction, 10 minutes, 30 minutes after reaction, and
This shows the power spectrum density after 60 minutes. 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 for detecting whether an antigen-antibody reaction has occurred or fixing the antigen concentration from changes in the power spectral density. There are many ways to do this, some of which are 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, the integral value Sa from frequency f ₁ to f ₂ is calculated for the spectral density curve A before the reaction, and the same frequency range f ₁ to f ₂ is also calculated for the power spectral density curve B after the reaction for a predetermined time. Find the integral value Sb. Next, find the ratio R ₁ =Sb/Sa. Values of such a ratio R ₁ are determined and stored in advance for various antigen concentrations, and the ratio R ₁ for a sample is determined, from which 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 power spectral density Ia before and after the reaction at a specific frequency f ₀ shown in Figure 9 is calculated. and Ib, respectively, and then their ratio R ₂ =Ib/Ia is determined. Even in this case, R ₂ is determined in advance for a sample with a known antigen concentration, and the concentration of the unknown antigen can be determined from the value of the ratio R ₂ determined for a sample with an unknown antigen concentration.

The third method is to determine the frequencies f _a and f _b 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 of the frequencies f _a and f _b of the rising part
R ₃ = f _b /f _a is determined, and the antigen concentration can be determined from the value of this ratio.

The present invention is not limited to the embodiments described above, but can be modified and changed in many ways. The above explanation has been given for immunoglobulin G (IgG), but immunoglobulin A (IgA), IgM, IgD,
It can be applied to the measurement of all substances that cause agglutination due to antigen-antibody reactions, such as IgE, Austrian antigen, syphilis antigen, and insulin. Also,
In the above-mentioned example, antibodies were immobilized on the surface of microparticles to detect antigens in the specimen.
Antibodies in a subject can also be detected by immobilizing antigens on the surface of microparticles. Furthermore, although polystyrene latex particles were used as the fine particles in the above embodiments, other organic particles or inorganic particles such as glass may also be used. Furthermore, in the above-mentioned example, fine particles were present in the antigen-antibody reaction solution from the beginning, but instead of using such fine particles, scattered light from fine particulate products generated as a result of the antigen-antibody reaction was used. You can also. 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, and blood cells, cells, microorganisms, etc. can also be used as particles. Furthermore, in the embodiment shown in Figure 1, a batch method was used in which the antigen-antibody reaction solution was stored in a cell and measurements were carried out, but it is of course also possible to use a hero method in which measurements are carried out while the antigen-antibody reaction solution is continuously flowing. It is possible.

Furthermore, in the above embodiments, a laser antigen that emits coherent light is used as the antigen, but an antigen 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 accuracy and reproducibility than non-labeled immunoanalytical methods such as immunoelectrophoresis, immunodiffusion, and precipitation, so it is possible to obtain highly reliable measurement results with high precision.

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

(4) Compared to methods that quantify 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 equipment is smaller and cheaper, and the measurement results are highly accurate and reliable. is obtained.

(5) Much useful information about antigen-antibody reactions can be obtained when measurements are made based on the power spectral density of optical fluctuations.

[Brief explanation of the drawing]

Figures 1a and b are conceptual diagrams showing the basic structure and operation of the immune reaction measuring method according to the present invention;
The figure 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, and FIG. A diagram showing the configuration of another embodiment of
Figure 5 is a graph showing the power spectrum density of the intensity fluctuation of scattered light from non-agglomerated particles, Figure 6 is a graph showing the power spectrum density of the intensity fluctuation of scattered light from aggregated particles, and Figures 7 and 8 are graphs showing the power spectrum density of the intensity fluctuation of scattered light from aggregated particles. The figures are graphs showing the power spectral density before and after the antigen-antibody reaction, Figures 9 and 10.
The figure is a graph for explaining a method of measuring antigen concentration from power spectral density. 1...Light source, 2...Lens, 3...Polarizer, 4
... Cell, 5 ... Reaction liquid, 6 ... Lens, 7 ...
Analyzer, 8... photodetector, 11... laser light source,
17...Polarizer, 18...Cell, 20...Reaction liquid, 21...Collimator, 22...Analyzer, 23
...Photodetector, 25...Data processing device, 26...
...Low noise amplifier, 27...Low pass filter, 2
8... A/D converter, 29... Fast Fourier transform unit, 30... Arithmetic processing unit, 31... Display device.

Claims (1)

[Claims] 1. Linearly polarized radiation is projected onto a reaction solution containing at least an antigen and an antibody, and light scattered by fine particles generated by an antigen-antibody reaction or antibodies or antigens added to the reaction solution are immobilized. Detecting the scattered light generated by the antigen-antibody reaction of the microparticles through an analyzer having a polarization plane perpendicular to the polarization plane of the radiation, and measuring the antigen-antibody reaction based on this detection output. A method for measuring an immune response characterized by: 2. Claim 1, characterized in that 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.
The immunoreaction measurement method described. 3. Light is projected onto a reaction solution containing at least an antigen and an antibody, and light is scattered by microparticles generated by the antigen-antibody reaction or scattering caused by the antigen-antibody reaction of antibodies added to the reaction solution or microparticles on which the antigen is immobilized. An apparatus for detecting light and measuring an antigen-antibody reaction based on the power spectral density of intensity fluctuations of the detection output, comprising: a cell containing a reaction solution for performing the antigen-antibody reaction; 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; 1. An immune reaction measuring device using linearly polarized light, comprising means for receiving an output signal, determining the power spectrum density of the intensity fluctuation, and measuring an antigen-antibody reaction based on the power spectrum density.