Fig 2: MSCs Activate MAIT Cells by Secreting IL-15(A) The relative mRNA expression of several cytokines in MSCs was measured using quantitative real-time PCR. MSCs expressed IL-6, TGF-ß, IL-7, and IL-15 at high levels, but not IL-10, IL-12, IL-18, IL1-ß, or IFN-a. MSCs cocultured with MAIT cells expressed higher levels of IL-15 than MSCs cultured alone.(B) ELISA detection of the culture supernatants from MSCs showed that MSCs secreted IL-7 and IL-15. MSCs cocultured with MAIT cells expressed higher levels of IL-15, but not IL-7, than MSCs cultured alone.(C–F) All groups of MAIT cells were cultured with CD3/CD28 antibodies. IL-15 blockade reversed the increases in CD69 (C), TNF-a (D), IFN-? (E), and GB (F) expression in MAIT cells activated by MSCs, while IL-7 blockade did not exert an obvious effect (C–F). n = 12 independent experiments; **p < 0.01; ns, not significant.