Heinonen Krista M, Perreault Claude
Institute for Research in Immunology and Cancer; Department of Medicine, Universite de Montreal, Montreal, QC, Canada H3C 3J7.
Crit Rev Immunol. 2008;28(5):441-66. doi: 10.1615/critrevimmunol.v28.i5.40.
Although vertebrate hematopoiesis is known to occur in a variety of locations, the differentiation of T lymphocytes takes place only in the thymus. Conversely, the only known function of the thymus is to produce T lymphocytes. As thymic function progressively diminishes with age in all individuals, and decreased thymic capacity has been linked to an impaired resistance to infections and cancer, increasing thymic function and/or extrathymic T-cell development could thus play an important role in health management in elderly subjects. However, it is currently unclear why the thymus is essential for T-cell development and precisely what is necessary to make a functional T lymphopoietic organ. In this review, we shall discuss the current literature on the similarities and differences between thymic and extrathymic T cells. A major conclusion is that innate T cells can be generated extrathymically, but only the thymus can support the development of classic adaptive T cells. Functional differences between thymic and extrathymic T cells provide a rationale for conservation of the thymus as the sole primary T lymphoid organ. These differences also have implications for the management of thymus involution.
虽然已知脊椎动物的造血作用发生在多种部位，但T淋巴细胞的分化仅在胸腺中进行。相反，胸腺唯一已知的功能就是产生T淋巴细胞。由于在所有个体中，胸腺功能会随着年龄的增长而逐渐衰退，且胸腺功能的下降与抗感染和抗癌能力受损有关，因此增强胸腺功能和/或胸腺外T细胞的发育可能在老年个体的健康管理中发挥重要作用。然而，目前尚不清楚胸腺为何对T细胞发育至关重要，以及打造一个功能性T淋巴细胞生成器官究竟需要什么条件。在这篇综述中，我们将讨论目前有关胸腺T细胞和胸腺外T细胞异同的文献。一个主要结论是，先天性T细胞可在胸腺外生成，但只有胸腺能够支持经典适应性T细胞的发育。胸腺T细胞和胸腺外T细胞之间的功能差异为胸腺作为唯一主要T淋巴细胞器官得以保留提供了理论依据。这些差异对胸腺退化的管理也具有启示意义。
