Early tumor influx of MHC-II-positive monocytes observed in all treatment groups, is in line with previously reported association between an increase in blood MHC-II-positive monocytes and improved responses to anti-PD1 in patients with metastatic melanoma [35]; after recruitment into tumors, such monocytes can act as antigen-presenting cells directly, differentiate into inflammatory CD11c-high tumor-associated macrophages that favor T-cell recruitment and activation [36], and/or differentiate into dendritic cells, enhancing antigen presentation and consequently local immune recognition [37]. Here, PDCD1 is linked to metastatic melanoma.