CD39 Is Expressed on Functional Effector and Tissue-resident Memory CD8+ T Cells

The ecto-ATPase CD39 is expressed on exhausted CD8+ T cells in chronic viral infection and has been proposed as a marker of tumor-specific CD8+ T cells in cancer, but the role of CD39 in an effector and memory T cell response has not been clearly defined. We report that CD39 is expressed on Ag-specific CD8+ short-lived effector cells, while it's co-ectoenzyme, CD73, is found on memory precursor effector cells (MPECs) in vivo. Inhibition of CD39 enzymatic activity during in vitro T cell priming enhances MPEC differentiation in vivo after transfer and infection. The enriched MPEC phenotype is associated with enhanced tissue resident memory T cell (TRM cell) establishment in the brain and salivary gland following an acute intranasal viral infection, suggesting that CD39 ATPase activity plays a role in memory CD8+ T cell differentiation. We also show that CD39 is expressed on human and murine TRM cells across several nonlymphoid tissues and melanoma, whereas CD73 is expressed on both circulating and resident memory subsets in mice. In contrast to exhausted CD39+ T cells in chronic infection, CD39+ TRM cells are fully functional when stimulated ex vivo with cognate Ag, further expanding the identity of CD39 beyond a T cell exhaustion marker.