Immunochemical studies of the a allotypes of rabbit heavy chain variable regions—I.

Radioimmunoassays using purified and labeled anti-a3 antibodies were developed and used to study a3 allotypic determinants on normal IgGs and anti-polysaccharide antibodies of restricted heterogeneity. Our results provide additional evidence for differences in fine specificity of al anti-a3 and a2 anti-a3. Insights into the causes and nature of allotypic heterogeneity have come from the recognition that some a3 allotypic determinants on normal IgGs and restricted IgGs may bind anti-a3 antibodies with different average association constants. A purified fraction of a2 anti-a3 which cross-reacts with a1 IgG was found advantageous for assaying an a3 IgG of restricted heterogeneity. The use of this fraction (a2 anti-a3 CRI) for assays of peptides derived from the a3 heavy chain is described in a subsequent paper.