Of particular interest and possible importance, some recent studies demonstrated that M2-polarized MPs can express key immunotherapeutic targets, such as checkpoint proteins (e.g., PD-1) that appear to be involved in T-cell activation, as well as targets of other specific checkpoint-blocking immunotherapies (anti-PD-1/PDL-1) currently of interest as part of new therapeutic paradigms for understanding the conceptual basis for chemotherapy-resistant neoplasms. The gene discussed is PDCD1; the disease is neoplasm.