IL-6–mediated rescue of the functional deficiency of Tipe2 ^−/− MDSCs. (A) Expression levels of the indicated proteins in WT and Tipe2^−/− tumor-derived MDSCs as determined by immunoblotting (left) and densitometric analysis of the immunoblots (right). (B) Histograms of CD126 and CD130 expression by CD45⁺CD11b⁺Gr-1⁺ tumor-derived MDSCs from WT and Tipe2^−/− B16F10 tumor-bearing mice. (C) Tumor growth in WT and Tipe2^−/− mice injected with mock or IL-6–expressing B16F10 cells. (D) T cell suppression by tumor-derived MDSCs from WT and Tipe2^−/− mice injected s.c. with mock or IL-6–expressing B16F10 cells, at an MDSC:T cell ratio of 1:4. (E) Expression levels of the indicated proteins as determined by immunoblotting in tumor-derived MDSCs from WT and Tipe2^−/− mice injected s.c. with mock or IL-6–expressing B16F10 cells. Data are means ± SEM and are from a representative experiment of three; n = 6 mice per group (A, B, D, and E) or n = 10 mice per group (C). Unpaired Student’s t test for A–D. ***, P < 0.001; ****, P < 0.0001; ns, not significant.