Degree of heterogeneity of binding specificities of antibodies to the phenylarsonate group that share a common idiotype.

We have investigated the microheterogeneity of hybridoma products (HP) expressing the major idiotype (CRIA) associated with A/J antibodies to the p-azophenylarsonate (Ar) hapten group. The properties investigated were affinity for a phenylarsonate derivative and the fine specificity of the combining sites of the various HP. The fine specificity was approached by measuring relative affinities for a series of related haptens. It was found that, although variations exist, there are strong similarities in affinities and fine specificities of the antigen-binding sites of CRI+A HP. The range of affinities for (p-azobenzenearsonic acid)-N-3H-acetyl-L-tyrosine was 0.41 x 10(6)-2.2 x 10(6) M-1. In all cases the addition of a second ring structure (benzene or histidine) and an azo group greatly increased the binding affinity. Some differences in fine specificity among the HP were seen with respect to affinities for o-arsanilate or the arsanilate derivative of histidine. However, the two HP which are the strongest inhibitors in the conventional assay for CRIA were virtually identical to one another and to induced A/J anti-Ar antibodies in their fine specificities. Together with previous data on amino acid sequences and serological properties, the results indicate that, despite their microheterogeneity, members of the CRIA family are closely related in structure and hapten-binding specificity.