CD103 hi T reg cells constrain lung fibrosis induced by CD103 lo tissue-resident pathogenic CD4 T cells

Tissue-resident memory T cells (T RM cells) are crucial mediators of adaptive immunity in nonlymphoid tissues. However, the functional heterogeneity and pathogenic roles of CD4 + T RM cells that reside within chronic inflammatory lesions remain unknown. We found that CD69 hi CD103 lo CD4 + T RM cells produced effector cytokines and promoted the inflammation and fibrotic responses induced by chronic exposure to Aspergillus fumigatus . Simultaneously, immunosuppressive CD69 hi CD103 hi Foxp3 + CD4 + regulatory T cells were induced and constrained the ability of pathogenic CD103 lo T RM cells to cause fibrosis. Thus, lung tissue-resident CD4 + T cells play crucial roles in the pathology of chronic lung inflammation, and CD103 expression defines pathogenic effector and immunosuppressive tissue-resident cell subpopulations in the inflamed lung.