LAUSR

Whether induced tissue-resident memory T (TRM) cells in nonlymphoid organs alone can mediate allograft rejection is unknown. By grafting alloskin or heart into severe combined immunodeficient or Rag2KO mice in which a piece of induced CD4+ and/or CD8+ TRM cell–containing MHC-matched or syngeneic skin was transplanted in advance, we addressed this issue. The induced CD4+ TRM cells in the skin alone acutely rejected alloskin or heart grafts. RNA-seq analysis showed that induced CD4+ TRM cells in skin favorably differentiated into TH17-like polarization during the secondary immune response. Inhibition of the key TH17 signaling molecule RORγt attenuated TRM cell–mediated graft rejection. Thus, we offer a unique mouse model to specifically study TRM cell–mediated allograft rejection without the involvement of lymphocytes in lymphoid organs and tissues. Our study provides strong evidence supporting the hypothesis that long-lived alloreactive TRM cells resident in other organs/tissues substantially contribute to organ allograft rejection.