Genetic control of the immune response to staphylococcal nuclease. IX. Recombination between genes determining BALB/c antinuclease idiotypes and the heavy chain allotype locus.

The genetic linkage relationship of two antinuclease idiotypes produced by the BALB/c strain was investigated in the backcross (BALB/c x CB.20) X CB.20. These two idiotypes were detected by Lewis rat anti-idiotypic antisera prepared against affinity-purified A/J and SJL antinuclease antibodies, termed the A/J and SJL idiotypes, respectively. Both idiotypes were found to be linked to the IgCHa immunoglobulin heavy chain allotype locus. There was, however, a high frequency of recombination observed between both markers and the IgCHa locus, with eight of 83 backcross animals recombinant for the A/J idiotype and five of 83 recombinant for the SJL idiotype. All such recombinant animals were IgCHb/b homozygotes that had gained one or both idiotypes. These results are consistent with a genetic map of VHr region genes in the BALB/c strain in which genes determining the SJL idiotype are closer to the IgCHa allotype locus than are genes determining the A/J idiotype. This high frequency of recombination may indicate that the chromosome segment containing VH region genes is very large or that it has structural features that promote recombination.