Isolation and mapping of the rabbit DM genes

Proper peptide presentation by major histocompatibility complex (MHC)-encod ed class II antigens is dependent on the products of the MHC DM loci. We id entified the rabbit orthologues (RLA-DMA and -DMB) of human HLA-DMA and -DM B and found that they have 76.9% and 78.8% identity with HLA-DMA and -DMB, respectively. Like classical class II MHC genes, RLA-DM genes are more clos ely related to human HLA-DM genes than to mouse H2-DM. Among the DM family, there is a high degree of variability at the amino terminus of the DMa cha ins, and length variability in the cytoplasmic tails of both DMa and DM bet a, The rabbit DM genes are coexpressed with class II genes in lymphoid tiss ues, as are the DM genes of other mammals. The RLA-DM locus maps to the cla ss II region of the rabbit MHC, and is flanked by the DP and DOE loci. Desp ite having some similarities to class II genes of bony fishes, the DM famil y represents a separate branch of the MHC class II family.