Divergent results in radial immunodiffusion. III. Isolation and specificity test of class-specific antibodies.

A method is described for the isolation of antibodies specific for immunoglobulin class determinants from antisera containing antibodies both for the immunoglobulin class and for its subclasses, using affinity chromatography. The model system used is bovine IgG with its subclasses IgG1 and IgG2, together with antisera raised in goats and sheep. The specificity of the isolated class-specific antibodies was demonstrated by double diffusion (DI) and radial immunodiffusion (RID). The levels of total IgG in normal bovine sera measured with the class-specific antibodies were the same as the sum of the IgG1 and IgG2 levels obtained with subclass-specific antisera. However, sera from cattle infected with Fasciola hepatica contain IgG1 fragments without class-specific determinants. In these sera, contrary to expectation, the class-specific antibodies gave higher total IgG levels than the subclass-specific antisera. The yield of class-specific antibodies varied with different batches of antisera. The minimum amount of each class-specific antibody preparation needed for a RID plate also varied. Class-specific antibodies isolated from antisera raised against IgG1 gave more intense precipitation reactions in RID against IgG1 than IgG2 and vice versa. Possible reasons for these differences are discussed.