Secretion of Monospecific Anti-Hapten IgG Antibodies by Rabbit Immunocytes

Abstract

A direct search was made for antibody-forming cells that simultaneously secrete antibodies to two related but non-cross-reacting hapten determinants. This was accomplished by combining the hapten-specific hemolytic plaque technique with the replica immune plaque procedure. Rabbits were immunized intravenously with a particulate immunogen consisting of pigeon erythrocyte membranes coupled with both p-arsanilate and o-sulfanilate determinants. Replica immune hapten-specific plaque assays were performed after immunization intervals of 10 days, 4 months and 6 months. These replica assays showed two separate and distinct populations (anti-p-arsanilate and anti-o-sulfanilate) of IgG-secreting immunocytes. No more than 2% of the 6 × 10³ immunocytes screened were potential double secretors, and the average number for all assays was 1.4%. It was possible to artificially produce a similar small percentage (2.5%) of “double” plaques by intentionally mixing two independent monospecific plaque-forming cell suspensions. The study indicates that at any one time the vast majority of IgG-secreting rabbit splenic immunocytes are specialized for the production of antibodies that react with only one of two noncross-reacting hapten determinants.