Radial immunodiffusion - أطلس مختبرات العرب

Single radial immunodiffusion allows quantitation of antigens. Antibody is added to the agar gel which is then poured onto slides and allowed to set. Wells are punched in the agar and standard volumes of test antigen of different concentration are put in the wells. The plates are left for at least 24 hours, during which time the antigen diffuses out of the wells to form soluble complexes (in antigen excess) with the antibody. These continue to diffuse outwards, binding more antibody until an equivalence point is reached and the complexes precipitate in a ring. The area within the precipitin ring, measured as ring diameter squared, is proportional to the antigen concentration. Unknowns are derived by interpolation from the standard curve (graph). The whole process may be reversed using an antigen-containing gel to determine unknown concentrations of antibody.