Ouchterlony test
Immune precipitates can form in an agar matrix. When antigen and antibody diffuse toward one another in agar, or when antibody is incorporated into the agar and antigen diffuses into the antibody containing matrix, a visible line of precipitation will form. As in a precipitation reaction in fluid, visible precipitation occurs in the region of equivalence, whereas no visible precipitate forms in regions of antibody or antigen excess. This immunodiffusion reaction can be used to determine relative concentrations of antibodies or antigens, to compare antigens or to determine the relative purity of an antigen preparation.
In the Ouchterlony method both antigen and antibody diffuse radially from wells toward each other, thereby establishing a concentration gradient. As equivalence is reached, a visible line of precipitation forms. This is a simple and effective qualitative tool for determining the relationship between antigens and the number of different Ag-Ab systems present.
