CD274 and neoplasm: Macrophages exert immunosuppressive functions through expression of anti-inflammatory molecules, such as PD-L1.44 In 4T1-bearing AhrflflLyz2Cre+/− mice, we observed a significant decrease of PD-L1 expression on macrophages from the PMN, but not from the primary tumor sites (Fig. 3a and Supplementary Fig. S4a, b).