Hansen Victoria L, Miller Robert D
Department of Biology, Center for Evolutionary and Theoretical Immunology, University of New Mexico, Albuquerque, NM, 87131, USA.
Results Probl Cell Differ. 2015;57:265-78. doi: 10.1007/978-3-319-20819-0_11.
The T cell receptor structure and genetic organization have been thought to have been stable in vertebrate evolution relative to the immunoglobulins. For the most part, this has been true and the content and organization of T cell receptor genes has been fairly conserved over the past 400 million years of gnathostome evolution. Analyses of TCRδ chains in a broad range of vertebrate lineages over the past decade have revealed a remarkable and previously unrealized degree of plasticity. This plasticity can generally be described in two forms. The first is broad use of antibody heavy chain variable genes in place of the conventional Vδ. The second form containing an unusual three extracellular domain structures has evolved independently in both cartilaginous fishes and mammals. Two well-studied vertebrate lineages, the eutherian mammals such as mice and humans and teleost fishes, lack any of these alternative TCR forms, contributing to why they went undiscovered for so long after the initial description of the conventional TCR chains three decades ago. This chapter describes the state of knowledge of these unusual TCR forms, both their structure and genetics, and current ideas on their function.
相对于免疫球蛋白，T细胞受体的结构和基因组织在脊椎动物进化过程中被认为是稳定的。在很大程度上，确实如此，在过去4亿年的有颌类动物进化过程中，T细胞受体基因的内容和组织一直相当保守。在过去十年中，对广泛脊椎动物谱系中的TCRδ链进行的分析揭示了一种显著且此前未被认识到的可塑性程度。这种可塑性通常可以两种形式来描述。第一种是广泛使用抗体重链可变基因来替代传统的Vδ。第二种形式包含一种不寻常的三个细胞外结构域结构，在软骨鱼类和哺乳动物中均独立进化。两个经过充分研究的脊椎动物谱系，如小鼠和人类等真兽类哺乳动物以及硬骨鱼类，缺乏任何这些替代性TCR形式，这也解释了为什么在三十年前首次描述传统TCR链之后这么久它们才被发现。本章描述了这些不寻常TCR形式的知识现状，包括它们的结构和遗传学，以及关于其功能的当前观点。
