Figure 1. Human MAIT cells dose-dependently inhibit the in vitro proliferation of alloreactive T cells.
(A) MLR was performed using total or MAIT-depleted CFSE-labeled PBMCs (“responders”) cocultured for 6 days with irradiated allogeneic PBMCs (“stimulators”). Proliferation was quantified as the percentage of CFSElo cells in non-MAIT (Vα7.2–tetramer–) responder T cells on day 6. Left panel shows a representative example, and the graph indicates the percentage of proliferating T cells in paired total or MAIT-depleted PBMCs (n = 10 different recipient/donor pairs). (B–D) FACS-sorted purified MAIT cells were added to the MLR at different MAIT/MAIT-depleted PBMC ratios. (B) Representative staining in the absence (ctrl) or presence of MAIT cells at 1:1 ratio. (C) Percentage of inhibition of responder T cell proliferation in the presence (versus absence) of MAIT cells purified from autologous (responder-derived) or allogeneic (stimulator-derived) PBMCs (n = 6 independent experiments). (D) Inhibition of proliferation by MAIT cells was analyzed separately in CD4+ and CD8+ responder T cells (n = 7 independent experiments). (E) Purified CFSE-labeled CD4+ T cells were cultured with allogeneic CD3– PBMCs in the presence of purified MAIT cells or effector memory CD8 T cells (non-MAIT CD8+CD45RA–CCR7– TEM cells, CD8EM) at the indicated MAIT (or CD8EM)/CD4+ T cell ratios. Results are shown as mean ± SEM (C–E). *P 0.05, **P 0.01, ***P 0.001, ****P 0.001, from paired t tests (A) or 2-way ANOVA followed by Holm-Šídák multiple comparisons test (D and E).