Kasahara M, Vazquez M, Sato K, McKinney E C, Flajnik M F
Department of Microbiology and Immunology, University of Miami School of Medicine, FL 33101.
Proc Natl Acad Sci U S A. 1992 Aug 1;89(15):6688-92. doi: 10.1073/pnas.89.15.6688.
Along with the T-cell receptor and immunoglobulin, the major histocompatibility complex (MHC) plays a key role in mounting immune responses to foreign antigen. To gain insights into the evolution of the MHC, class II A cDNA clones were isolated from nurse sharks, a member of the class of cartilaginous fish. Two closely related cDNA clones, which might encode allelic products, were identified; of the three amino acid substitutions found in the alpha 1 domain, two were located at positions postulated to interact with processed peptides. The deduced nurse shark MHC class II alpha chains showed conspicuous structural similarity to their mammalian counterparts. Isolation of cDNA clones encoding typical MHC class II alpha chains was unexpected since no direct evidence for T-cell-mediated immune responses has been obtained in the cartilaginous fish. The cartilaginous fish is phylogenetically the most primitive class of vertebrates from which any MHC gene has been isolated.
主要组织相容性复合体（MHC）与T细胞受体和免疫球蛋白一起，在对外来抗原产生免疫反应中起关键作用。为了深入了解MHC的进化，从软骨鱼类的护士鲨中分离出II类A cDNA克隆。鉴定出两个密切相关的cDNA克隆，它们可能编码等位基因产物；在α1结构域中发现的三个氨基酸取代中，有两个位于假定与加工后的肽相互作用的位置。推导的护士鲨MHC II类α链与其哺乳动物对应物显示出明显的结构相似性。编码典型MHC II类α链的cDNA克隆的分离出乎意料，因为在软骨鱼类中尚未获得T细胞介导的免疫反应的直接证据。软骨鱼类在系统发育上是已分离出任何MHC基因的最原始的脊椎动物类别。
