Since a previous study demonstrated that the phagocytotic ability of PD-1+ macrophages was impaired in colorectal cancer [8], we next determined the phagocytotic ability of both PD-1+ and PD-1− macrophages obtained from GC tissue using Zymosan A. Our results demonstrated that Zymosan A uptake by PD-1+ macrophages was significantly less than that by PD-1− macrophages, indicating that the phagocytotic ability of PD-1+ macrophages obtained from GC tissue was impaired (P = 0.0079, Fig. 4). Here, PDCD1 is linked to gastric cancer.