Central memory T (T_CM) cells patrol lymph nodes and perform conventional memory responses on restimulation: proliferation, migration and differentiation into diverse T cell subsets while also self-renewing. Resident memory T (T_RM) cells are parked within single organs, share properties with terminal effectors and contribute to rapid host protection. We observed that reactivated T_RM cells rejoined the circulating pool. Epigenetic analyses revealed that T_RM cells align closely with conventional memory T cell populations, bearing little resemblance to recently activated effectors. Fully differentiated T_RM cells isolated from small intestine epithelium exhibited the potential to differentiate into T_CM cells, effector memory T cells and T_RM cells on recall. Ex-T_RM cells, former intestinal T_RM cells that rejoined the circulating pool, heritably maintained a predilection for homing back to their tissue of origin on subsequent reactivation and a heightened capacity to redifferentiate into T_RM cells. Thus, T_RM cells can rejoin the circulation but are advantaged to re-form local T_RM when called on.

中央记忆 T (T _CM ) 细胞巡逻淋巴结，并在再刺激时执行传统的记忆反应：增殖、迁移和分化为不同的 T 细胞亚群，同时进行自我更新。常驻记忆 T ( _TRM ) 细胞驻留在单个器官内，与末端效应器共享特性，有助于快速保护宿主。我们观察到重新激活的 T _RM细胞重新加入循环池。表观遗传学分析表明， _TRM细胞与传统记忆 T 细胞群密切相关，与最近激活的效应细胞几乎没有相似之处。从小肠上皮分离的完全分化的 T _RM细胞表现出分化为 T _CM细胞、效应记忆 T 细胞和回忆时 T _RM细胞的潜力。 Ex-T _RM细胞，即重新加入循环池的前肠道 T _RM细胞，在随后的重新激活中遗传性地保持了回归其起源组织的倾向，并且具有增强的再分化为 T _RM细胞的能力。因此， _TRM细胞可以重新加入循环，但有利于在需要时重新形成局部_TRM 。