| Research Abstract |
The specific aims of this project were i) to clarify the phylogenetic origin of the major histocompatibility complex (MHC) by cloning MHC genes of lower vertebrates, and ii) to identify general rules that govern the long-term evolution of the MHC.As to the first specific aim, we demonstrated that the cartilaginous fish has typical, polymorphic MHC genes.However, all attempts to isolate MHC genes from cyclostomes were unsuccessful, suggestimg that these animals might not have bona fide MHC genes.As to the second specific aim, we identified the following three rules that apply to MHC genes in general.First, overall domain organization of MHC genes is very well conserved in evolution despite the fact that the sequence conservation is poor.Second, the number of functionally important, polymorphic MHC genes shows little interspecies variation and falls between one and three per haplotype.Third, essential features of MHC polymorphism are well conserved in evolution.
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