Contribution of the VK4 light chain to antibody specificity for lysozyme and beta (1,6)D-galactan

The VL amino acid sequence of an anti-lysozyme hybridoma protein, HyHEL-5, was determined. HyHEL-5 expresses a V region of the VK4 family and JK1. The VK4 family also includes light chains from galactan binding antibodies, although sequence comparisons suggest that a different member of this family is used to encode HyHEL-5. The HyHEL-5 light chain has a deletion of residue 96, such that L3 is one residue shorter than the majority of murine L3. Chain recombination experiments, employing H and L chains from different anti-galactan and anti-lysozyme binding antibodies, were performed to examine the contribution of the H and L chain in dictating specificity for either galactan or the lysozyme epitope recognized by HyHEL-5. The results indicate that, although the ability to bind galactan vs lysozyme is absolutely heavy-chain dependent, having the appropriate heavy chain is not sufficient for specific high affinity binding. Both the L chains from HyHEL-5 and J539 (a galactan-binding myeloma protein) were capable of supporting binding to galactan in combination with the J539 H chain, but affinity for galactan is less with the HyHEL-5 L chain. Only VK4 L chains supported binding of the HyHEL-5 heavy chain to the HyHEL-5 epitope, although binding with the J539 L chain was low affinity and relatively nonspecific.