Structural studies on induced antibodies with defined idiotypic specificities. IX. Framework differences in the heavy- and light-chain-variable regions of monoclonal anti-p-azophenylarsonate antibodies from A/J mice differing with respect to a cross-reactive idiotype.

Abstract

Amino terminal amino acid sequence analyses were performed on the H and L chains of induced monoclonal antibodies with specificity for the hapten p-azophenylarsonate. Four of the 8 antibodies reacted with conventional antisera to the previously described A/J anti-arsonate cross-reactive idiotype (CRI). Of the 16 chains analyzed, all but one contained sequence differences in their first framework segment (residues 1-30) that distinguished them from the H- and L-chain sequences found in anti-arsonate antibodies isolated from A/J serum or ascites fluid. The presence of such framework differences appeared to be independent of whether or not the hybridoma antibodies bear the CRI. In spite of the framework substitutions, all 4 of the CRI-positive hybridoma antibodies had variable (V)-region frameworks that were very similar to each other and to the CRI-positive molecules found in A/J serum. Two of the 4 CRI-negative molecules were also structurally similar to the serum antibodies. Two others, however, were strikingly different from any serum anti-arsonate antibody thus far described and appeared to reflect a completely separate repertoire of anti-arsonate antibodies in the A/J mouse. In addition, serological analyses with an anti-idiotypic antiserum generated against a CRI-positive hybridoma product suggested that each monoclonal antibody may possess individual antigenic specificities different from the determinant(s) detected with the conventional rabbit anti-CRI. The consistent appearance of framework substitutions in what has been thought to be a homogeneous antibody population has important implications for our understanding of the generation of antibody diversity and for the precise chemical definition of an idiotype.