Center for Evolutionary and Theoretical Immunology, Department of Biology, University of New Mexico, Albuquerque, NM.
Department of Orthopedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester, Rochester, NY.
J Immunol. 2022 Apr 15;208(8):1960-1967. doi: 10.4049/jimmunol.2101158. Epub 2022 Mar 28.
T lymphocytes or T cells are key components of the vertebrate response to pathogens and cancer. There are two T cell classes based on their TCRs, αβ T cells and γδ T cells, and each plays a critical role in immune responses. The squamate reptiles may be unique among the vertebrate lineages by lacking an entire class of T cells, the γδ T cells. In this study, we investigated the basis of the loss of the γδ T cells in squamates. The genome and transcriptome of a sleepy lizard, the skink were compared with those of tuatara, the last living member of the Rhynchocephalian reptiles. We demonstrate that the lack of TCRγ and TCRδ transcripts in the skink are due to large deletions in the genome. We also show that tuataras are on a growing list of species, including sharks, frogs, birds, alligators, and platypus, that can use an atypical TCRδ that appears to be a chimera of a TCR chain with an Ab-like Ag-binding domain. Tuatara represents the nearest living relative to squamates that retain γδ T cells. The loss of γδTCR in the skink is due to genomic deletions that appear to be conserved in other squamates. The genes encoding the αβTCR chains in the skink do not appear to have increased in complexity to compensate for the loss of γδ T cells.
T 淋巴细胞或 T 细胞是脊椎动物对病原体和癌症反应的关键组成部分。根据其 TCR，T 细胞分为两类，αβ T 细胞和 γδ T 细胞，每一类在免疫反应中都起着关键作用。爬行动物蜥蜴类可能是脊椎动物谱系中独一无二的，因为它们缺乏一类 T 细胞，即 γδ T 细胞。在这项研究中，我们研究了蜥蜴类失去 γδ T 细胞的基础。将睡蜥蜴的基因组和转录组与圆舌蜥（Rhynchocephalian reptiles 的最后一个现存成员）的基因组和转录组进行了比较。我们证明，睡蜥蜴中缺乏 TCRγ 和 TCRδ 转录物是由于基因组中的大片段缺失所致。我们还表明，圆舌蜥属于越来越多的物种之列，包括鲨鱼、青蛙、鸟类、短吻鳄和鸭嘴兽，它们可以使用一种非典型的 TCRδ，这种 TCRδ 似乎是 TCR 链与 Ab 样 Ag 结合域的嵌合体。圆舌蜥是保留 γδ T 细胞的蜥蜴类最近的活体亲属。睡蜥蜴中 γδTCR 的缺失是由于基因组缺失所致，这种缺失似乎在其他蜥蜴类中是保守的。睡蜥蜴中编码 αβTCR 链的基因似乎并没有变得更加复杂，以弥补 γδ T 细胞的缺失。
