Adult B-cell repertoire is biased toward two heavy-chain variable-region genes that rearrange frequently in fetal pre-B cells.

Fetal pre-B cells rearrange a very restricted set of immunoglobulin variable genes for the heavy chain (VH). To determine whether the adult B-cell repertoire is similarly skewed, we first identified the genes that rearrange in pre-B cells from BALB/c mice and then determined their frequency of rearrangement in adult B cells. In fetal pre-B cell lines, two genes, VH81X from the 7183 subfamily and VHOx2 from the Q52 subfamily, comprise 75% of the rearranged alleles of an estimated 1000 genes (P less than 0.001). Sequencing analyses revealed that rearrangements involving the two genes were both productive and nonproductive. The biased rearrangement of these two VH genes persists in B-cell hybridomas from adult mice at a frequency of 22%, as determined by Southern gel analysis and RNA sequencing. The sequence of one VHOx2 rearrangement from a hybridoma shows that the rearrangement is productive, suggesting that the gene encodes an antibody that could participate in the immune response. The data indicate that the adult B-cell repertoire is not random concerning usage of individual VH genes, and it may be shaped by the unknown mechanisms that cause preferential rearrangement of certain genes early in ontogeny.