Conservation and divergence of immunoglobulin VH pseudogenes.

The 12 immunoglobulin VH pseudogenes, that have been characterized to date, differ from most pseudogenes of other multigene families in two aspects: (i) they carry only one (11 cases) or at the most two (1 case) deleterious mutations and (ii) they show no evidence of increased divergence from intact VH genes. We describe here the first immunoglobulin VH pseudogene that does not have these characteristics. This pseudogene accumulated numerous deleterious mutations and diverged considerably from other genes of the VH gene family to which it belongs. In possible contrast to the other VH pseudogenes, this pseudogene seems to be selectively neutral. We discuss the implications of the characterization of this diverged VH pseudogene in relation to our understanding of the genetic mechanisms that generate diversity among germline immunoglobulin VH genes.