Skin-resident memory CD8 ⁺ T cells trigger a state of tissue-wide pathogen alert

Resident memory T cells sound the alarm Immunological memory protects against reinfection. Resident memory T cells (T RM ) are long-lived and remain in the tissues where they first encountered a pathogen (see the Perspective by Carbone and Gebhardt). Schenkel et al. and Ariotti et al. found that CD8 + T RM cells act like first responders in the female reproductive tissue or the skin of mice upon antigen reencounter. By secreting inflammatory proteins, T RM cells rapidly activated local immune cells to respond, so much so that they protected against infection with an unrelated pathogen. Iijima and Iwasaki found that CD4 + T RM cells protected mice against reinfection with intravaginal herpes simplex virus 2. Science , this issue p. 98 , p. 101 , p. 93 ; see also p. 40