In this comprehensive review of tissue-resident memory T (TRM) cells, Amsen et al. discuss the properties that define this recently uncovered and distinct T cell lineage, how they are generated and maintained, and their role in fighting solid tumors. Often marked by CD103 expression, TRM cells adapt to and reside in a specific tissue environment where they persist long term to protect against recurrent threats. These adaptations, along with their ability to adhere to their tissue of residence, grant TRM cells unique “home field” advantage for battling solid tumors that could one day be exploited for immunotherapy.
Immune responses in tissues are constrained by the physiological properties of the tissue involved. Tissue-resident memory T cells (TRM cells) are a recently discovered lineage of T cells specialized for life and function within tissues. Emerging evidence has shown that TRM cells have a special role in the control of solid tumors. A high frequency of TRM cells in tumors correlates with favorable disease progression in patients with cancer, and studies of mice have shown that TRM cells are necessary for optimal immunological control of solid tumors. Here we describe what defines TRM cells as a separate lineage and how these cells are generated. Furthermore, we discuss the properties that allow TRM cells to operate in normal and transformed tissues, as well as implications for the treatment of patients with cancer.