Molecular analysis and fine specificity of antibodies against an organophosphorus hapten

We have identified four fine specificity groups reactive with the organophosphorus hapten Soman among 46 hybridomas generated in specific response to immunization with Soman-keyhole limpet hemocyanin (KLH). The different fine specificity groups do not appear to correlate with the use of particular V genes. Molecular analysis of VH genes demonstrates predominant use of VH J558 family members in hybridomas of all fine specificity groups although several different VH genes within this family as well as others are able to contribute. Diversity of VH gene usage was also apparent in primary IgM-producing hybridomas. In contrast, there appears to be restricted L chain usage; a large number (18/46) used the Vκ1 family. Interestingly, the Vκ1 family also plays an important role in the memory response to phosphocholine (PC)-KLH, a related organophosphate hapten which shares several structural features with Soman, particularly when coupled to protein carriers. The Vκ1C gene appears to predominate in the PC-KLH response. Restriction analysis of DNA from the Vκ1-positive Soman-KLH-specific hybridomas suggests that a single Vκ1 gene may be utilized by 17/18 but that this gene is different from Vκ1C and may be Vκ1A. We propose that members of the Vκ1 family contribute favorably in generating combining sites that recognize all or part of the structural features shared by the two haptenic structures Soman and PC when they are coupled to protein. This most likely involves recognition of the phenyl linker moiety as the dominant feature. It appears that the L chain rather than the H chain may play a more significant role in forming this phenyl-Soman-specific combining site and perhaps the combining sites for phenyl or ring structures in general.