CD274 and neoplasm: Generally, an adaptive immune resistance mechanism is the upregulation of PD-L1 expression on tumor cells or tumor-associated macrophages (TAMs) or dendritic cells induced by inflammatory cytokines from tumor-infiltrating T cells [13]; chemokines or cytokines secreted by these T cells also recruit immunosuppressive M2 macrophages or Tregs or myeloid-derived suppressor cells (MDSCs) into tumors [14,15].