CD274 and neoplasm: The immunosuppressive function of M2-type TAMs is achieved through a multidimensional mechanism: on the one hand, its highly expressed PD-L1 on the surface binds to T cell PD-1 and inhibits T cell activity, thus helping the tumour cells to escape from immunosurveillance; on the other hand, it facilitates immune escape through the secretion of immunosuppressive cytokines (e.g., IL-10, TGF-β) and the inhibition of T cell function [44–46].