PDCD1 and neoplasm: Intriguingly, PD-1 deletion in myeloid cells (PD-1f/fLysMcre mice) effectively delays tumor growth, similar to that observed during global deletion of PD-1, whereas deletion of PD-1 in T cells (PD-1f/fCD4cre mice) is less effective.119 These results indicate a crucial role for PD-1 in inhibiting the antitumor immunity of myeloid cells.