Immunogenicity of anti-idiotypic antibodies and of their F(ab′) 2 fragments

Abstract

Within the idiotype/anti-idiotype network, immunoglobulins act alternatively as reactive molecules and as antigens. To investigate the antigenic properties of immunoglobulins, we evaluated the immunogenicity in rabbits of three murine monoclonal anti-idiotypic antibodies and of their F(ab′) 2 fragments. These antibodies, bearing the internal image of a human melanoma antigen, may be useful in view of a human therapeutic application. The effect was evaluated as specific anti-anti-idiotypic response, related to the immunogenicity of the idiotypic epitopes in the combining sites of the immunoglobulins, and as total anti-murine immunoglobulin response, which represents the recognition of all the immunological determinants of the molecule. The results showed that the administration of the F(ab′) 2 fragments results in either higher or similar degrees of anti-anti-idiotypic immunization, compared to those induced by the whole immunoglobulins. Nevertheless, when anti-anti-idiotypic immunogenicity was increased, the anti-murine response did not increase proportionally. This suggests that the use for in vivo administration of F(ab′) 2 fragments is more convenient than the use of their original molecules, since this results, at least, in a similar or eventually in an increased specific immunogenicity, while the possibility of aspecific recognition is reduced.