Gordon et al. [121] observed increased expression of programmed cell death protein 1 (PD-1) on the cell surface of CAF-induced M2 macrophages, with subsequent studies indicating that TAMs with high PD-1 expression can suppress the innate and adaptive anticancer immune responses, including reducing their own phagocytic potency against tumor cells and preventing T-cell infiltration and proliferation [118]. Here, PDCD1 is linked to neoplasm.