Restricted utilization of germ-line VH genes and diversity of D regions in rabbit splenic Ig mRNA

Previous studies have suggested that the majority of rabbit germ-line VH genes encode molecules that are rarely found in serum or secretory Ig. To examine the repertoire of expressed VH genes, we prepared a cDNA library from splenic mRNA of an alpha 1/alpha 1 rabbit and isolated 10 complete VH-encoding cDNA clones. None of the cDNA clones hybridized to an oligomer that had hybridized to more than 50% of cloned germ-line VH genes. These data indicate that only a subset of germ-line VH genes are used in functional VDJ rearrangements. DNA sequence analysis demonstrated that the 10 cDNA clones contained highly similar VH regions, further suggesting that the repertoire of utilized VH genes is limited. In contrast, the D regions of each of the 10 clones exhibited little similarity to one another, suggesting that the rabbit has a large D region repertoire. We propose that the apparent lack of diversity within the VH segment of VDJ rearrangements is offset by extensive D region diversity.