Interstrain conservation of the murine GAT-specific antibody V kappa repertoire as analyzed at the germline gene level.

A cDNA library was constructed in pBR322 from mRNA encoding an anti-GAT (Glu60 Ala30 Tyr10) monoclonal antibody kappa chain. Two cDNA clones were extensively characterized. One, L XI 62, was derived from an aberrant V kappa-J kappa rearrangement which resulted in a frame-shift at position 96, leading to a stop codon at the very beginning of the constant region. The second, L XIX 27, 1150 bp long, was unequivocally assigned to a GAT-specific kappa chain, by comparison of its nucleotide sequence with the previously determined NH2-terminal amino acid sequence of the isolated kappa chain. A specific probe, containing the leader and most of the V kappa gene-encoded region, was prepared from this clone and hybridized to EcoRI and BamHI restriction fragments of liver (unrearranged) DNA extracted from the BALB/c, DBA/2 and C57BL/6 mouse strains. Under stringent conditions, similar patterns were observed for all three strains, and consisted of a small number of bands (3-5). Under nonstringent conditions, patterns were again very similar when the different strains were compared, although 15-20 bands could be identified. These observations support the hypothesis that the GAT-specific kappa chains found in antibodies expressing the public CGAT idiotypes are encoded by a very small number of germline genes. This V kappa repertoire seems extremely conserved between the three strains that were analyzed, an observation which correlates with the interstrain conservation of these public idiotypic specificities.