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Infection with influenza virus results in the deposition of anti-influenza CD8+ resident memory T cells (TRM cells) in the lung. As a consequence of their location in the lung mucosal tissue, these cells are exposed to cytopathic pathogens over the life of the organism and may themselves be susceptible to infection. Here we found that lung TRM cells selectively maintained expression of the interferon-induced transmembrane protein IFITM3, a protein that confers broad resistance to viral infection. Lung TRM cells that lacked IFITM3 expression were more susceptible to infection than were their normal counterparts and were selectively lost during a secondary bout of infection. Thus, lung TRM cells were programmed to retain IFITM3 expression, which facilitated their survival and protection from viral infection during subsequent exposures. [ABSTRACT FROM AUTHOR]

Effective immunity is dependent on long-surviving memory T cells. Various memory subsets make distinct contributions to immune protection, especially in peripheral infection. It has been suggested that T cells in nonlymphoid tissues are important during local infection, although their relationship with populations in the circulation remains poorly defined. Here we describe a unique memory T cell subset present after acute infection with herpes simplex virus that remained resident in the skin and in latently infected sensory ganglia. These T cells were in disequilibrium with the circulating lymphocyte pool and controlled new infection with this virus. Thus, these cells represent an example of tissue-resident memory T cells that can provide protective immunity at points of pathogen entry. [ABSTRACT FROM AUTHOR]