MR1 and neoplasm: In concordance with the activation of MAIT cells (TCR-MR1 or IL-12/18 cytokine), they likely elicit direct (MAIT cell to tumor cell) and indirect (MAIT cell to non-MAIT cell or IL-12/18 cytokine competition) effects, regulating host anti-tumor immunity in a TME-specific manner (74, 101).