Germline structure and differential utilization of Igha and Ighb VH10 genes

Abstract

Ab heavy chains encoded by mouse VH10 genes have been of particular interest due to their frequent association with DNA binding. We reported previously that VH10 sequences are over-represented in the preimmune repertoire considering the apparent number of germline-encoded VH10 gene segments. In this report, we show that the VH10 family consists of three and two germline genes in the Igha and Ighb haplotypes, respectively. The complete nucleotide sequences of these five genes, including promoters and recombination signal sequences, were determined and allow unambiguous assignment of allelic relationships. The usage of individual VH10 genes varied significantly and ranged from 0.2% to an extraordinary 7.2% of the VH genes expressed by splenic B cells. Since the promoter and recombination signal sequence elements of all five VH10 genes are identical, we suggest that the few amino acid differences encoded by these five germline VH10 genes determine their representation in the preimmune repertoire. Rearrangements of the most frequently used VH10 gene have an apparent bias for histidine at position 95 of complementarity-determining region-3 (CDR3). These CDR3s are also biased for asparagine, an amino acid associated with the CDRs of DNA binding Abs. Together, these results suggest that high VH10 gene use is the result of B cell receptor-mediated selection and may involve DNA and/or ligands that share antigenic features with DNA.