Fig. 2. Lack of IFNAR1 does not alter immune-suppressive activity by PMN-MDSCs.

a Expression of interferon response genes in MDSC. PMN and monocytes were isolated by cell sorting from the spleen of naïve mice (Naïve SP) or spleen (TUM SP) and tumors (TUM) of EL4-bearing mice. Irf7 and Isg15 expression were quantified by qRT-PCR in each cell population. Each dot represents a single mouse. Mean and SD is shown. In PMN-MDSC: n = 6 for Naïve SP Irf7, n = 4 for TUM SP Irf7, n = 5 for TUM Irf7, n = 8 for Naïve SP Isg15, n = 4 for TUM SP, n = 5 for TUM Isg15. In M-MDSC: n = 4 for Naïve SP Irf7 group, n = 6 for TUM SP and TUM groups, n = 4 for Naïve SP Isg15, n = 6 for TUM SP Isg15, n = 6 for TUM Isg15. P values were calculated in the ANOVA test with corrections for multiple comparisons. b Suppression assay of PMN-MDSCs and M-MDSCs isolated from both spleen and tumors of tumor-bearing mice. PMN-MDSCs (n = 4) and M-MDSCs (n = 3) from spleen or tumor were cocultured with antigen-specific CD8⁺ T cells (OT-1 splenocytes) at different ratios. T cell proliferation was evaluated in triplicate using [³H]-thymidine uptake and presented as a percentage based on positive control (without MDSCs), set as 100% proliferation. c Suppression assay (as in a) of splenic PMN-MDSC and M-MDSC treated for 2 h with 2000 U of IFNβ. (n = 3). Mean and SD is shown. d PMN and Mon were isolated from bone marrow (BM) of tumor-free WT or Ifnar1 KO mice. Suppression assay was performed as described in (b). e Percentage and an absolute number of PMN-MDSCs and M-MDSCs in the spleen of tumor-bearing mice. Mean and SD is shown. n = 3. f Suppressive activity of PMN-MDSCs from spleen and tumors. N = 3 for spleen, n = 2 for tumor. A representative of three experiments. 100%—proliferation in the absence of MDSC. In all panels, data are expressed as mean ± SD and the p values were calculated using unpaired two-sided Student’s t test, except when otherwise indicated. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. ns not significant.