immunodiffusion

(immunology) A serological procedure in which antigen and antibody solutions are permitted to diffuse toward each other through a gel matrix; interaction is manifested by a precipitin line for each system.

A technique for the identification and quantification of any of the immunoglobulins.

A technique for studying reactions between antigens and antibodies by observing precipitates formed by the combination of specific antigens and antibodies that have diffused in a gel in which they have been separately placed.

The diffusion of antigen and antibody from separate wells, usually cut in agar, such that precipitation lines form in the agar between the wells.

• radial i. (Mancini technique) — antigen diffuses into the agar which contains specific antibody and a ring of precipitate is formed, the diameter of which is directly proportional to the concentration of the antigen and can thereby be used to quantitate the amount of antigen. A reverse radial immunodiffusion test, in which antigen is incorporated in the agar, can be used to quantitate the amount of antibody in a sample.
• i. tests — include double immunodiffusion (Ouchterloney technique) which is used in the coggins test for equine infectious anemia and single immunodiffusion (Oudin technique), as well as radial immunodiffusion.