ST2–IL-33 signaling enhances cytolytic molecules expression and cytolytic activity. (A) Cytolytic assays: B6 or C3H.SW T cell MLR cultures were co-cultured with C3H.SW-derived MLL-AF9 leukemic cells for 6 h (n = 4, from two independent experiments, unpaired t test; data are shown as mean ± SEM; **, P < 0.01). (B) Cytolytic assays. CD4 or CD8 purified from B6 or C3H.SW T cell MLR cultures were co-cultured with C3H.SW-derived MLL-AF9 cells for 6 h (n = 4, from four independent experiments, unpaired t test; data are shown as mean ± SEM; **, P < 0.01). (C) Cytolytic assay of B6 WT or IL-9^−/− T9_IL-33 cells differentiated under MLR conditions. After 5 d, WT or IL-9^−/− T9_IL-33 cells were incubated with BALB/c MLL-AF9 cells for 6 h (n = 3, from three independent experiments, unpaired t test; data are shown as mean ± SEM; ***, P < 0.001). (D) mRNA expression of Egfr on BALB-5047, MLL-AF9 cells by quantitative PCR (left). Syngeneic T9_IL-33, WT T9_IL-33, or ST2^−/− T9_IL-33 cells were differentiated in MLR conditions and co-cultured with BALB/c MLL-AF9 cells for 6 h at a ratio of 10:1 with anti-AREG (right; n = 3, unpaired t test; data are shown as mean ± SEM). (E) Representative plots of human GzmB and perforin expression in human T9 and T9_IL-33 cells, and bar graphs showing the frequencies of GzmB⁺ and GzmK⁺ cells (n = 3, from three independent experiments, unpaired t test; data are shown as mean ± SEM; *, P < 0.05; **, P < 0.01). (F) Cytolytic assays of human T9 or T9_IL-33 cells incubated for 6 h with MOLM14 leukemia cells (n = 3, from three independent experiments, unpaired t test; data are shown as mean ± SEM; **, P < 0.01; ***, P < 0.001).