Mouse histocompatibility-related genes are not conserved in other mammals.

In addition to the genes for classical H-2 antigens, the H-2 complex of the mouse contains numerous homologous genes belonging to several distinct families. It is not known whether they have any functions. To address this question, I have investigated whether these genes are separately conserved in evolution. Subcloned 5' gene segments, encoding the variable domains, were used as hybridisation probes on genomic DNA blots of various mammals. Only the largest gene family, which includes the classical H-2/HLA genes, is detectable in humans and other mammals. The other gene families, including Qa-2 and T1a, are not conserved even in rodents. Most or all of their coding sequences are therefore redundant.