Isolation of a rat immune response gene identical to an alleged mouse a class II beta-chain pseudogene

A human HLA-DQ beta-chain cDNA was used as a probe to identify and isolate a rat major histocompatibility antigen beta-chain gene from a genomic library constructed in the vector lambda Charon 28 using Wistar rat DNA (RT1u). The isolated exon of the rat gene (RT1.B beta 2) encoding a beta-chain second domain was found to share 93% nucleotide homology with a mouse A beta 2 exon. Although the genomic organization of this gene is consistent with the hypothesis that it represents a pseudogene, the remarkable preservation of a specific sequence favors the view that this class II antigen beta-chain gene has retained its coding function.