ONLY SELECTED LIGHT-CHAINS COMBINE WITH A GIVEN HEAVY-CHAIN TO CONFERSPECIFICITY FOR A MODEL GLYCOPEPTIDE ANTIGEN

The M and N human blood group glycopeptide Ags are carried on RBCs by glycophorin A. Previous results suggested that the murine humoral immu ne response against the N, but not the hi, Ag is restricted. In additi on, these results suggested that particular highly homologous heavy ch ains might be able to combine promiscuously with various light chains to yield anti-N specificity. To examine this, the current study used F ab phage methodology to couple an array of light chains, obtained from cDNA libraries isolated from immunized mice, to single Fd obtained fr om N61, N92, and 425/2B hybridomas, Interestingly, for the chimeric Fa b to retain M or N specificity, the new light chains needed to belong to the same V-k gene family as the light chain from the parental, hybr idoma-derived mAb, In some cases the new light chains modified the Fab affinity and fine. specificity. For example, library-derived light ch ains coupled with the N92 Fd yielded chimeric Fab with increased affin ity. In particular, the affinity of these univalent chimeric Fab for t he N Ag was equivalent to that of the bivalent parental IgG mAb, Taken together, these results demonstrate that particular structures formed by the light chain V region are required to cooperate with a particul ar heavy chain V region to create a functional binding site for these glycopeptide Ags, They also demonstrate a lack of heavy chain promiscu ity in the formation of murine anti-M and anti-N Abs.