Characterization of human rheumatoid factors with seven antiidiotypes induced by synthetic hypervariable region peptides.

Abstract

Recently, synthetic peptides corresponding to the complementarity-determining regions (CDR) of Ig molecules were used to induce antiidiotypic antisera. Peptide PSH3, representing the 3rd CDR of the IgM rheumatoid factor (RF) Sie H chain, induced a private antiidiotype that reacted with only 1 out of 5 IgM-RF. Peptide PSL2, corresponding to the 2nd CDR of Sie L chain, induced an antibody against a crossreactive idiotype (CRI), expressed by 10 out of 12 human IgM-RF analyzed. Five additional antiidiotypic antibodies were generated by immunization with synthetic peptides identical to the 3rd L chain CDR of IgM-RF Sie (PSL3), the 2nd and 3rd H chain CDR of IgM-RF Wol, and the 2nd and 3rd CDR of IgM-RF Pom. As analyzed by immunoblot assay, both anti-PSL3 and anti-PSL2 reacted with the majority of 16 IgM-RF. All 5 antiidiotypes induced by the H chain peptide reacted only with the parent proteins, except anti-PSH3, which reacted weakly with one additional RF. Evidently, one (or very few) VL gene(s), but a larger number of VH genes, are used to encode IgM-RF autoantibodies.