Formation and function of tissue-resident memory T cells during viral infection.

Memory T cells are an important component of the adaptive immune response. Tissue-resident memory T cells (TRM) are a recently described subset of memory T cells that reside in peripheral tissues and are maintained independently of circulating subsets of memory T cells. Importantly, TRM are frequently found in barrier tissues that commonly serve as entry portals for pathogens such as viruses. Mounting evidence shows that TRM are superior to their circulating counterparts in conferring protective immunity against a wide range of viruses. In this review, we will discuss the role of TRM in controlling viral infection with a focus on CD8+ TRM, the factors that regulate differentiation and a potential role for TRM in future vaccine development.