The alpha chain gene of H-2O has an unexpected location in the major histocompatibility complex

A previously unknown major histocompatibility complex class II molecule consisting of the beta chain encoded by the H-2Ob gene and an unknown alpha chain was recently described. We now report that the alpha chain occurs in two allelic forms distinguished by charge difference. Using inbred recombinant mouse strains we were able to map the H-2Oa gene to a location between the A.TL and B10.MBR recombination points. Cosmids covering this region were used to isolate the gene. Sequence analysis revealed that the H-2Oa gene is the murine equivalent of the human HLA- DNA gene. These results indicate that the human HLA-DNA gene, the existence of which has long been known, is indeed coding for DO alpha, the alpha chain pairing with DO beta.