MHC homology between various mammalian species at the DNA level: its relevance to MHC evolution

Considerable homology concerning the major histocompatibility complexes of man, rhesus monkey, dog, cat, cow, sheep, rabbit and goat has been established by Southern blot analyses. Human cDNAs from both class I and class II gene products were used as probes. Besides the expected hybridization of the probes to human DNA, the probes displayed a clear affinity for the other DNAs as well. Equal numbers of bands-about 16 depending on the enzyme used - appear in digests of human and rhesus monkey DNA when the class I cDNA is used as a probe. This number is slightly smaller and varying in the other species. The same holds for class II probes. Both class I and class II probes show no detectable homology at all with Xenopus DNA under the conditions used. A substantial MHC homology at the DNA level between man and rhesus monkey can be concluded from these data, this homology being somewhat smaller in various other species. Further implications for the evolution of MHC are discussed.