Molecular Evolution of Major Histocompatibility Complex and T Cell Receptor Genes

本研究的主要目的是通过克隆低等脊椎动物的主要组织相容性复合体（major histocompatibility complex，MHC）基因来阐明MHC的系统发育起源，以及确定支配MHC长期进化的一般规律。因此，我们认为这些动物可能没有真正的MHC基因。至于第二个具体目标，我们确定了以下三个规则，适用于MHC基因一般。第一，总体结构域的MHC基因是非常保守的进化，尽管事实上，序列保守性差。第二，功能重要的，多态性的MHC基因在种间变异很小，每个单倍型的福尔斯在1到3个之间。

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.