PDCD1 and neoplasm: In addition, various cellular activities such as activation, phagocytosis, migration, invasion, and EMT of a variety of immune cells (such as B cells, macrophages, DC, NK cells) and non-immune cells (such as fibroblasts, epithelial cells, various tumor cells) have also been found to be regulated by PD-1/PD-L1 axis (Figure 5).