Idiotypic regulation of mouse anti-H-2 antibody responses. I. induction of 5936-idiotype-bearing Ig molecules upon immunization with H-2k alloantigen.

Mouse-immunoglobulin (MIg) tolerant rabbits immunized with mouse H-2 antibodies produced anti-idiotype antisera, which were reactive towards specific B- and T-cell receptors. One such rabbit antiserum (from rabbit 5936) defines a family of idiotypes (Id) designated 5936-idiotypes (Rubin et al. 1979). The present experiments were performed in order to establish (1) the nature of 5936-Id+ serum molecules, (2) the specificity of 5936-Id+ serum molecules, (3) the association of the 5936-Id genes to allotype and/or H-2 genes and (4) the immunological role of 5936-Id+ serum molecules. A sensitive radioimmunoassay employing 125I-labelled-F(ab)2 fragments of B6 anti-B10.BR MIg pool, 5936 antiserum, and a sheep anti-rabbit immunoglobulin antiserum, was used.--The results suggested that 5936-Id+ serum molecules were exclusively MIg, and that they were mainly of the IgG1 class. Such molecules were induced in B6 mice (H-2b/Ig-1b) upon immunization with H-2k but not with H-2q alloantigen or conventional antigens. The 5936-Id were found to be associated with Ig-1b allotypes and the H-2b complex may contain immune response (Ir) genes which, in comparison with Ir genes in H-2d and H-2s, favor the expression of 5936-Id.--Adsorption of 5936-Id+ B6 anti-CBA MIg preparations on CBA (IAk) spleen cells demonstrated that CBA antibodies were 5936-Id-. It is discussed whether 5936-Id+, IgG1 molecules in B6 anti-CBA sera are anti-(anti-CBA) antibodies or nonspecific antibodies, the production of which is augmented by immunization with IAk alloantigen.