1. A laboratory method of identifying antigens in the blood by creating an artificial antigen antibody reaction.
2. Immunodiffusion in which the antigens are separated according to their migration in an electric field.

Immunodiffusiion is the technique for analyzing antigen (a protein molecule that often protrudes from the surface of a cell which can induce an immune response) and antibody mixtures by watching them as they diffuse toward each other within a support medium (usually a gel).