The molecular basis of the persistence of experienced T lymphocytes, also known as “memory T lymphocytes,” is still enigmatic. We are beginning to understand their considerable heterogeneity and topographic compartmentalization into memory T cells circulating through the body and those residing in a particular tissue. In some tissues, like murine spleen, subpopulations of memory T cells proliferating in the absence of antigen (homeostatic proliferation) have been described. Other populations are maintained resting in terms of transcription, mobility, and proliferation in dedicated survival niches organized by stromal cells. The survival of these memory T cells is conditional on being in such a niche, where they can persist for a lifetime. Circulating memory T lymphocytes of distinct immune responses slowly decline in numbers over time. The rules governing their entry into and exit from blood, as well as their lifestyle outside of the blood and their relation to resident memory T cells are poorly understood. Homeostasis of circulating, proliferating, and resting memory T cells is obviously controlled by different rheostats: tissue-exit and tissue-entry signals for circulating and proliferation-inducing signals for proliferating memory T cells. For tissue-resident, resting memory T cells, it is the availability of their survival niche. Apparently, this mechanism (i.e., the link between memory T cell and stromal cell) is so robust that it provides efficient T-cell memory over a lifetime in tissues such as the bone marrow.

中文翻译：

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T 细胞记忆的稳态和持久性——静息和不安定 T 细胞记忆

有经验的 T 淋巴细胞（也称为“记忆 T 淋巴细胞”）持续存在的分子基础仍然是个谜。我们开始了解它们在体内循环的记忆 T 细胞和驻留在特定组织中的记忆 T 细胞的显着异质性和拓扑区划。在一些组织中，如小鼠脾脏，记忆 T 细胞亚群在没有抗原的情况下增殖（稳态增殖）。其他群体在由基质细胞组织的专用生存环境中的转录、移动性和增殖方面保持静止。这些记忆 T 细胞的生存取决于它们能否在这样的环境中生存一生。随着时间的推移，具有不同免疫反应的循环记忆 T 淋巴细胞数量缓慢下降。人们对它们进入和离开血液的规则、它们在血液之外的生活方式以及它们与常驻记忆 T 细胞的关系知之甚少。循环、增殖和静息记忆 T 细胞的稳态显然由不同的变阻器控制：循环的组织退出和组织进入信号以及增殖记忆 T 细胞的增殖诱导信号。对于组织驻留的静息记忆 T 细胞来说，关键在于其生存环境的可用性。显然，这种机制（即记忆 T 细胞和基质细胞之间的联系）非常强大，以至于它在骨髓等组织中提供了终生有效的 T 细胞记忆。循环、增殖和静息记忆 T 细胞的稳态显然由不同的变阻器控制：循环的组织退出和组织进入信号以及增殖记忆 T 细胞的增殖诱导信号。对于组织驻留的静息记忆 T 细胞来说，关键在于其生存环境的可用性。显然，这种机制（即记忆 T 细胞和基质细胞之间的联系）非常强大，以至于它在骨髓等组织中提供了终生有效的 T 细胞记忆。循环、增殖和静息记忆 T 细胞的稳态显然由不同的变阻器控制：循环的组织退出和组织进入信号以及增殖记忆 T 细胞的增殖诱导信号。对于组织驻留的静息记忆 T 细胞来说，关键在于其生存环境的可用性。显然，这种机制（即记忆 T 细胞和基质细胞之间的联系）非常强大，以至于它在骨髓等组织中提供了终生有效的 T 细胞记忆。