Fig. 5. Tumor microenvironment induces downregulation of IFNAR1 in MDSCs.

a IFNAR1 levels on bone marrow PMN (left) or Mon (right) treated for 18 h with 20% TES in vitro. (n = 4 untreated PMN, n = 5 TES treated PMN, n = 2—Mon). p Value was calculated in unpaired two-sided Student’s t test. b IFNβ and IFNα amount in eight different types of TES measured by ELISA. c Expression of IFNAR1 on PMNs, isolated from healthy donors’ blood (n = 3), treated for 16–18 h with 6 different TES (30%) and 30% PCI-30 tumor-conditioned media (TCM) in vitro. N = 3. p Values were calculated in a one-way Anova test with correction for multiple comparisons. d IFNAR1 levels on CD34-derived PMNs or Mon treated with 30% TES at day 7 followed by flow cytometry analysis on day 8 (n = 6). e BM PMNs (n = 3) were cultured in 0.5% O₂ (hypoxia) or 20 µM lactic acid for 16–18 h before measuring IFNAR1 levels by flow cytometry. In d, e, p values were calculated in unpaired two-sided Student’s t test. f IFNAR1 levels on BM PMNs or Mon treated for 16–18 h with different doses of ER stress inducer thapsigargin (THG; 2 μM, 1 μM, or 0.5 μM) in vitro (n = 3). p Values were calculated in a one-way ANOVA test with corrections for multiple comparisons. g PMN were isolated from BM of naïve WT or SA mice, treated overnight with 1 µM of THG. THG has then washed away and suppressive activity of the cells was measured by coculturing PMN with PMEL splenocytes stained with cell trace Far-red at different ratios and stimulated with the cognate peptide (gp100, 10 ng/ml). Cell trace dilution was measured after 48 h to assess the proliferation of CD8⁺ T cells (n = 3). p Values were calculated in one-way ANOVA test with corrections for multiple comparisons. h PMN were isolated from BM of naïve WT or SA mice pretreated for 2 h with 2000 U/ml IFNβ then overnight with 1 µM of THG. Suppressive activity of the cells was measured by coculturing PMN with PMEL splenocytes stained with Cell trace Far-red and stimulated with the cognate peptide (gp100, 10 ng/ml). Cell trace dilution was measured after 48 h to assess the proliferation of CD8+ T cells (n = 3). In all figures, data are expressed as mean ± SD.