Figure 4.

IFN-γ production of NKT, not CD4+ T cells, was inhibited by myeloid-derived suppressor cells (MDSCs). (A) Wild-type (WT) and tumor-bearing (TB) mice were challenged by concanavalin A (Con A) (10 mg/kg body weight) 15 days post-B16 injections; 12 h later, mice were sacrificed and liver mononuclear cells were isolated. Afterward, intracellular IFN-γ intracellular staining was performed as described in Section “Materials and Methods,” and cells were analyzed by flow cytometry (n = 5). (B) One typical flow cytometry plot in panel (A) is shown. (C) MDSC depletion restored IFN-γ production of NKT cells. WT and TB mice were challenged by Con A 24 h after anti-Gr1 treatment. Then, 12 h later, mice were sacrificed and IFN-γ intracellular staining was performed, and cells were analyzed by flow cytometry (n = 5). (D) One typical flow cytometry plot in panel (C) is shown. (E) MDSC transfer inhibited IFN-γ production of NKT cells. 5 × 10⁵ TB MDSCs were intravenously transferred into WT mice, followed by Con A challenge (10 mg/kg), and 12 h later, livers were isolated. IFN-γ intracellular staining was performed, and cells were analyzed by flow cytometry (n = 5). (F) One typical flow cytometry plot in panel (E) is shown.