Analysis of molecular basis for allo-recognition

(1)分析了鲤科鱼类中编码MHC-I类分子的三个基因组基因和三个克隆，即银鱼和鲤鱼。由于这6个基因是通过α3区序列的同源性分离出来的，所以它们之间的氨基酸序列有70-90%的同源性。根据同源性的大小，它们可以分为四类。每个班级由几名到十多名成员组成。因此，这组MHC基因由30到40个成员组成。由于有几个组，在鲤科鱼类中至少有100个基因编码MHC-I类基因。(2)我们已经鉴定了弹性鲨(Shark)中编码MHC-I类分子的基因。其中一个基因编码一个典型的I类分子，由三个胞外结构域组成。Alpha1和Alpha2结构域的氨基酸序列与人和小鼠H2的氨基酸序列有40%~50%的同源性。这一结果表明，在弹簧类动物中存在典型的MHC-I类基因，并且α1和α2结构域的序列在从弹性脊椎动物到哺乳动物的进化过程中一直保持在较高的水平。(3)我们在人类HLA外分离到了一个新的编码MHC-I类分子的基因。MR1的α1和α2的氨基酸序列与人类白细胞抗原和小鼠H2，甚至与鸡MHC的氨基酸序列有40%~50%的同源性，既然我们已经分离到另一个基因MR2，那么在人类基因组中应该还有许多编码MHC I类基因的基因有待分析。这表明MHC基因的数量及其多样性比之前预期的要大得多。

(1) We have analyzed three genomic genes and three cDNA clones that encode MHC class I molecules in cyprinid fishes, namely the ginbuna crucian carp and the carp. Since these six genes have been isolated by the homology of the sequence of alpha3 domain, the amino acid sequences of the alpha3 domains showed 70-90% identities among them. Based on the extent of homology, they can be classified into four classes. Each of the class consists of several to more than ten members. Thus, this group of MHC genes is composed of 30 to 40 members. Since there are several groups, there are at least 100 genes that encode MHC class I genes in cyprinid fish.(2) We have characterized the genes encoding MHC class I-like molecules in elasmoblanchs (shark).One of the genes encodes a typical class I molecule that consists of three extra-cellular domains. The amino acid sequence of alpha1 and alpha2 domains showed 40 to 50 % identities to those of human HLA and mouse H2. This result idicated that a typical MHC class I gene exists in elasmoblanchs and that the sequences of alpha1 and alpha2 domains have been kept at a high degree during evolution from elasmobranch to mammalian.(3) We have isolated a new gene that encodes MHC class I-like molecule outside of human HLA.While HLA genes are encoded at human chromosome 6, a newly isolated gene, MR1, is encoded at chromosome 1q25. The amino acid sequence of alpha1 and alpha2 of MR1 showed 40 to 50 % identities to those of HLA and mouse H2, even chicken MHC.Since we have already isolated one more gene, MR2, there should be many other genes that encode MHC class I-like genes to be analyzed in human genome. This suggested that the number of MHC genes and their diversification was much larger than expected before.