All jawed vertebrates have four T cell receptor (TCR) chains expressed by thymus-derived lymphocytes that play a significant role in animal immune defense. However, avian TCR studies have been limited to a few species, although their co-functional major histocompatibility complexes (MHCs) have been studied for decades, showing various copy numbers and polymorphisms. Here, using public genome data, we characterized the copy numbers, the phylogenic relationship and selection of T cell receptor complex (TCR-C) segments, and the genomic organization of TCR loci across birds. Various numbers of C segments were found in the TCRα/TCRδ, TCRβ, and TCRγ loci, and phylogenetic analysis reflected both ancient gene duplication events (two Cβ segments and Cδ segments divergent into CδI and CδII) and contemporary evolution (lineage-specific and species-specific characteristics). Most passerines lack CδII segments and a second TRD locus, except Meliphagidae and Maluridae. A relatively stable structure was verified in four TCR loci of birds, except for the arrangement of V segment groups. In this study, we explored the phylogenetic relationships of TCR-C segments across avians for the first time. We inferred gene duplication and loss events during the evolution process. The finding of diverse TCR germline repertoires provides a better understanding of the immune systems of birds.

所有有颌脊椎动物都有由胸腺来源的淋巴细胞表达的四个 T 细胞受体 (TCR) 链，在动物免疫防御中发挥着重要作用。然而，鸟类 TCR 研究仅限于少数物种，尽管它们的协同功能主要组织相容性复合物 (MHC) 已被研究数十年，显示出不同的拷贝数和多态性。在这里，我们利用公共基因组数据，描述了 T 细胞受体复合物 (TCR-C) 片段的拷贝数、系统发育关系和选择，以及鸟类 TCR 位点的基因组组织。在 TCRα/TCRδ、TCRβ 和 TCRγ 位点中发现了不同数量的 C 片段，系统发育分析反映了古代基因复制事件（两个 Cβ 片段和 Cδ 片段分化为 CδI 和 CδII）和当代进化（谱系特异性和物种特异性）。 -具体特点）。大多数雀形目动物缺乏 CδII 片段和第二个 TRD 基因座，除了 Meliphagidae 和 Maluridae 之外。鸟类的4个TCR位点除V节段组的排列外均验证了相对稳定的结构。在这项研究中，我们首次探讨了鸟类 TCR-C 片段的系统发育关系。我们推断了进化过程中的基因复制和丢失事件。不同 TCR 种系库的发现有助于更好地了解鸟类的免疫系统。