TGF-β: Many Paths to CD103(+) CD8 T Cell Residency

CD8 tissue-resident memory T (T(RM)) cells primarily reside in nonlymphoid tissues without recirculating and provide front-line protective immunity against infections and cancers. CD8 T(RM) cells can be generally divided into CD69(+) CD103(−) T(RM) cells (referred to as CD103(−) T(RM) cells) and CD69(+) CD103(+) T(RM) cells (referred to as CD103(+) T(RM) cells). TGF-β plays a critical role in the development and maintenance of CD103(+) CD8 T(RM) cells. In this review, we summarize the current understanding of tissue-specific activation of TGF-β mediated by integrins and how it contributes to CD103(+) CD8 T(RM) cell development and maintenance. Furthermore, we discuss the underlying mechanisms utilized by TGF-β to regulate the development and maintenance of CD103(+) CD8 T(RM) cells. Overall, this review highlights the importance of TGF-β in regulating this unique subset of memory CD8 T cells that may shed light on improving vaccine design to target this population.