T cell lineages are defined by specialized functions and differential expression of surface antigens, cytokines and transcription factors. Conventional CD4⁺ and CD8⁺ T cells are the best studied of the T cell subsets, but ‘unconventional’ T cells have emerged as being more abundant and influential than has previously been appreciated. Key subsets of unconventional T cells include natural killer T (NKT) cells, mucosal-associated invariant T (MAIT) cells and γδ T cells; collectively, these make up ~10% of circulating T cells, and often they are the majority of T cells in tissues such as the liver and gut mucosa. Defects and deficiencies in unconventional T cells are associated with autoimmunity, chronic inflammation and cancer, so it is important to understand how their development is regulated. In this Review, we describe the thymic development of NKT cells, MAIT cells and γδ T cells and highlight some of the key differences between conventional and unconventional T cell development.

T细胞谱系由专门的功能和表面抗原，细胞因子和转录因子的差异表达来定义。常规CD4 ⁺和CD8 ⁺T细胞是T细胞亚群中研究最好的，但是“非常规” T细胞比以前所认识的更为丰富和有影响力。非常规T细胞的关键子集包括自然杀伤T（NKT）细胞，粘膜相关不变T（MAIT）细胞和γδT细胞。总的来说，它们构成了循环T细胞的约10％，通常它们是组织（例如肝脏和肠粘膜）中大多数T细胞。非常规T细胞的缺陷和缺陷与自身免疫，慢性炎症和癌症有关，因此了解如何调节其发育非常重要。在这篇综述中，我们描述了NKT细胞，MAIT细胞和γδT细胞的胸腺发育，并突出了常规和非常规T细胞发育之间的一些关键差异。