PDCD1 and neoplasm: In general, a suggested mechanism for adjuvant effects of TLR agonists is activating DCs [55], increasing efficacy of anti-CTLA-4 antibody [56], activating CD8+ T cells [57], M1 macrophages [58] and NK-cells [59], decreasing M2 macrophages and Tregs inside the tumor microenvironments [60,61], downregulating PD-1 expression on CD8+ T cells [62,63], and escaping anti-PD-L1 resistance [64].