An immunoglobulin VH pseudogene.

In the course of studying the members of the T15 group of VH gene segments, some of which participate in the immune response to phosphorylcholine in the mouse, we identified a VH gene segment that contains three mutations preventing its expression. The mutations are an in-frame stop codon, a 4-base insertion which causes a termination codon to be shifted into the reading frame, and a modification of the recognition elements involved in the joining of VH and D gene segments during variable region formation. This pseudogene, which is 88-96% homologous to the other members of the T15 VH gene group, is probably of relatively recent origin and will presumably be deleted from the VH gene family eventually. We suggest that pseudogenes can only arise in multigene families and that the occurrence of pseudogenes will be a relatively frequent phenomenon in these families. Because the antibody gene families are made up of multiple gene elements, undergo two types of DNA rearrangements during differentiation, and employ several different RNA splicing mechanisms for expression, there are many different ways a particular antibody gene segment may become a pseudogene.