Hydroxychloroquine polarized macrophages from the M2- to the M1-like state, which was characterized by spindle-shape, increased pseudopods, and upregulated iNOS expression in melanoma mice; moreover, it induced macrophages to release IFN-β, thereby inducing T cell-mediated cytotoxicity and notably increasing the ratio of M1 macrophages following combination therapy with PD-1 antibody (124). Here, PDCD1 is linked to melanoma.