Agar diffusion test

The agar diffusion test is a precipitation test of soluble antigen and corresponding antibodies in a semi-solid gel (agar or agarose) containing an electrolyte. Agar only acts as a grid in the experiment, and the water content is 99%. Soluble antigen and antibody can diffuse freely between them. If the antigen and antibody correspond, the ratio is appropriate, and a white precipitation line can be formed where they meet, which is a positive reaction. The precipitation line can be kept in a fixed position in the gel for a long time and can be stored after drying after staining. Precipitation lines (bands) are specifically impermeable to antigens and antibodies, while non-specific ones are not. Therefore, a precipitation line (band) represents the precipitation of an antigen and an antibody. Therefore, this test can analyze and study different antigen-antibody systems in solution.