Related to this, CD103+ TRM cells have been reported to have higher expression of inhibitory receptors such as CTLA4, Tim-3 and PD-1, as well as CD39.28 31 Likewise, CD103+CD39+ tumor-infiltrating CD8 T cells have been shown to be enriched for tumor-reactive cells and display exhausted gene signatures.32 This suggests that the role of CD103 on tumor-infiltrating T cells in cancer may be more complex than previously thought, and that tumor-reactive CD103+ TRMs may boost or inhibit the antitumor immune response. Here, CTLA4 is linked to cancer.