Exhausted-like CD8 resident memory T cells balance immunity and fibrotic sequelae

CD8 tissue-resident memory T cells (TRM) provide frontline immunity in mucosal tissues. The mechanisms regulating CD8 TRM maintenance, heterogeneity, protective and pathological functions are largely elusive. Here we identify an epitope-specific CD8 TRM population that is maintained by in situ MHC-I and B7 signaling following acute influenza infection. These TRM cells co-exhibit exhausted-like phenotypes and memory features, and provide heterologous immunity against secondary infection. PD-L1 blockade at the memory stage promotes exhausted-like TRM rejuvenation and secondary immunity at the cost of developing post-infection fibrotic sequelae. Increased numbers of CD8 TRM cells are observed in the lungs of pulmonary fibrosis patients compared to control patients. Thus, TRM exhaustion results from a tissue-specific cellular adaptation to balance fibrotic sequelae and secondary immunity. Examination of mRNA expression in NP and PA specific resident memory CD8 T cells in C57BL/6 mice.