Extract: The immune system is similar to the nervous system to some degree. Both systems are highly organized and orchestrated within multiple levels (molecular, cellular, and organ) and have memory capacity. Furthermore, both systems encounter environmental challenges: the nervous system receives social challenges whereas the immune system receives natural challenges. In contrast to the nervous system, where the functional units are connected by nerve fibers and the decisions are made by the brain, the immune response is based on collaboration between functional cellular and molecular units without permanent physical connection or instruction from a centralized organ. Nonetheless, in the immune system, antigen presenting cells (APCs) are some times considered commanders in the immune system whereas T cells, B cells, and NK cells are considered the soldiers. Antigen presenting cells can capture, process, and present antigens; and they initiate and induce antigen specific T cell immunity. Thus, antigen presenting cells are used as adjuvants to treat cancer. Recent studies demonstrated that these commanders, antigen presenting cells, are often found in the tumor microenvironment. Strikingly, these commanders (including macrophages, dendritic cells, and myeloid suppressor cells) in the tumor microenvironment are largely dysfunctional and induce T cell suppression (instead of stimulation) and tumor angiogenesis. Thus, depleting tumor environmental antigen presenting cells may be a novel therapeutic strategy in tumor immunotherapy.