LAUSR

Tissue-resident memory T cells (TRM cells) serve important roles in maintaining immunological defence at tissue barriers and by and large keep to their given tissue environment. In Science Immunology, Gratz and colleagues use a combination of human skin explants and xenotransplantation into immunocompromised mice to demonstrate that a small subset of CD4+ TRM cells can egress the skin and re-enter the circulation. These blood-borne cells have many of the phenotypic and transcriptomic characteristics of classic TRM cells but downregulate the C-type lectin CD69 to facilitate egress from the skin. TRM cells that have exited the skin can migrate systemically to seed distal skin sites. The precise trigger for this TRM cell migration and its physiological consequences remain unclear but might have important implications for the dissemination of immunity or immunopathology. ZF