THE IMMUNE RESPONSE TO AZO-PROTEIN CONJUGATES IN RABBITS UNRESPONSIVE TO THE PROTEIN CARRIERS

Abstract

Rabbits, made unresponsive to human serum albumin by means of antigen injections following total body X-irradiation, were immunized with sulphanil-azo conjugates of human serum albumin (HSA). Non-treated rabbits were similarly immunized with sulphanil-azo conjugates of rabbit serum albumin (RSA). Both groups reacted to the sulphanil-azo determinant, forming two types of antibodies. One cross-reacted with sulphanil-azo proteins of the homologous and two heterologous carriers; the other was specific to the conjugate of the homologous protein, although the animals were unresponsive to the homologous protein in its native state. In this respect, namely the immunological response to azo-protein conjugates, animals which are naturally tolerant to the protein carrier, and animals which were made tolerant to the protein carrier, are basically similar. The formation of antibodies specific to the homologous conjugates indicates that the hapten conjugation resulted in the formation of an antigenic determinant comprising both the haptenic group and part of the protein carrier. Upon further immunization with the hapten—protein conjugates, in rabbits tolerant to HSA, the tolerance to the protein carrier was abolished. Immunization of rabbits with sulphanil-azo RSA elicited antibodies which cross-reacted with HSA. The implication of these immune responses and reactions and their bearing on the mechanism of immune tolerance, and its breakdown, are discussed.