Structural studies on induced antibodies with defined idiotypic specificities--VIII. NH2-terminal amino acid sequence analysis of the heavy and light chain variable regions of monoclonal anti-para-azophenylarsonate antibodies from A/J mice differing with respect to a cross-reactive idiotype.

Monoclonal antibodies with specificity for the hapten p-azophenyl arsonate (Ar)^* were generated by somatic cell hybridization of A/J spleen cells and the non-secreting cell line, Sp2/0-Ag14, derived from a Balb/c myeloma. Of four hybridoma products examined, only one bore the previously described A/J anti-Ar cross-reactive idiotype (CRI). The heavy and light polypeptide chains of this CRI positive molecule along with one of of the CRI negative molecules were subjected to amino-terminal sequence analysis and compared with the induced CRI positive antibodies produced upon immunization of A/J mice. The results confirm the extremely restricted expression of V_H and V_L frameworks in the A/J anti-Ar population. Unexpectedly, when the hybridoma proteins were compared to the induced population of antibodies, from one to three amino acid substitutions were detected within the first framework segment (1–30) of each chain of both hybridoma products. The complete covalent structure of two monoclonal antibodies known to differ serologically only with respect to idiotype should prove useful in defining the exact structural basis of an idiotypic determinant.