Figure 9. IFNAR1 controls PD-L1 expression in MDSCs.

A. BM cells were cultured in the presence of GM-CSF (top panel) or AT3 tumor cell-conditioned medium for 4 days. These BM-derived CD11b⁺Gr1⁺ cells were analyzed for PD-L1 expression levels. PD-L1⁺ and PD-L1⁻ MDSCs were then analyzed for IFNAR1 expression level. Shown are representative results of one of three experiments. B. IFNAR1 MFIs of PD-L1⁺ and PD-L1⁻ MDSCs as shown in A were quantified. Column: mean; Bar: SD. C. Spleens and tumors were collected from AT3 mammary carcinoma-bearing mice (n=5). CD11b⁺Gr1⁺ cells were analyzed for PD-L1 expression levels. PD-L1⁺ and PD-L1⁻ MDSCs were then analyzed for IFNAR1 expression level. Shown are representative results of one of three tumor-bearing mice. D. IFNAR1 MFIs of PD-L1⁺ and PD-L1⁻ MDSCs as shown in C were quantified. Column: mean; Bar: SD. E. Spleens and tumors were collected from CT26 colon carcinoma-bearing mice (n=4). CD11b⁺Gr1⁺ cells were analyzed for PD-L1 expression levels. PD-L1⁺ and PD-L1⁻ MDSCs were then analyzed for IFNAR1 expression level. Shown are representative results of one of three tumor-bearing mice. F. IFNAR1 MFIs of PD-L1⁺ and PD-L1⁻ MDSCs as shown in E were quantified. Column: mean; Bar: SD. G–J. Tumors (G) and spleens (I) were collected from MC38 tumor-bearing WT (n=5) and IFNAR1 KO (n=5) mice and prepared for single cells. Cells were stained with CD11b-, Gr1, and PD-L1-specific mAbs and CD11b⁺Gr1⁺ cells were gated for PD-L1 expression levels. The PD-L1⁺ and PD-L1⁻ MDSCs were then analyzed for PD-L1 MFI. Shown are representative plots of one each of WT and IFNAR1 KO mice. The percentages of CD11b⁺Gr1⁺ cells and PD-L1⁺CD11b⁺Gr1⁺ cells in tumors (H) and spleens (J) of WT and IFNAR1 KO mice were quantified. The PD-L1 MFI of CD11b⁺Gr1⁺ from WT and IFNAR1 KO mice were also quantified. Column: mean; Bar: SD.