Table 2.

Effector function and immune stimulation by anti-PD-1 therapy

Cell Type	Effector Function
T cells	Enhanced proliferation of T-cell subsets (100) Increased expression of effector cytokines by infiltrating T cells (100) Elevated expression of IFN-γ and TNF-α (100) Increased tumor-infiltrating T cells (101) T cell-mediated antigen-specific immune response (93, 94, 100, 101)
Macrophages/monocytes	Increased tumor infiltration TAMs (tumor-associated macrophages) (53, 77, 84) Increase ratio of M1/M2 macrophages associated with improved prognosis and reduced tumor burden (53, 77, 84) Increase in phagocytosis of tumor cells (53, 77) Increase in IL-12 production and STAT1 activation (53, 102) Increased IL-6 production (53, 103)
Dendritic cells	Increased expression of CD40/CD40L, enhancing DC survival and resistance to apoptosis (93) Increased DC longevity (63) Recruit and prime T cells and stimulate local antitumoral response (93, 94) Increased secretion of IL-12 in response to anti-PD-1-activated T cells (94) Connect adaptive and innate immune cross talk and license immune response to tumor (57, 70)
Natural killer cells	Increased tumor infiltration (84, 104) Restored cytotoxic function after immune-dampening tumor microenvironment effect (104) Increased proliferation and differentiation (104) Increased production of granzyme B, perforin, and IFN-γ (104)

DC, dendritic cell; STAT1, signal transducer and activators of transcription 1.