Molecular characterization of bovine V lambda regions.

Using an inverse PCR technique with primers directed against constant region sequences, 18 V lambda regions have been isolated at random from bovine splenic cDNA for detailed analysis. On the basis of protein sequences in FR1 and their homologies to the human lambda chains NEWM and MCG, the bovine determinants can be separated into two families that have been designated V lambda 1 (94% of all clones isolated) and V lambda 2 (6% of all clones isolated). Scrutiny of the nucleotide sequences has allowed subdivision of the dominant family into V lambda 1a, V lambda 1b and V lambda 1c groupings, which represent 29, 65, and 6% of all V lambda 1 clones respectively. It appears that the size of CDR1 is V lambda group-specific--the region comprises 14 amino acids in V lambda 1a determinants and 13 residues in V lambda 1b and V lambda 1c,--whereas with a single exception, seven amino acids make up CDR2. The size of CDR3 is variable, ranging from 10 to 15 amino acids in length. Conservation of those nucleotide sequences that encode the signal peptide and FR3 has enabled us to amplify and characterize 14 V lambda 1 genes from kidney genomic DNA. Interestingly, half of the germline sequences were not represented in the data gathered from splenic cDNA, while the remaining genes could be identified as members of the V lambda 1a and V lambda 1b groups. The findings indicate that the V lambda 1 family dominates the expressed bovine light chain repertoire but that a large proportion of the germline segments from which this repertoire is derived may be nonfunctional.