The term "system of macrophages" can be accompanied by several synonyms including mononuclear phagocyte system, reticuloendothelial system, and myeloid-derived suppressor cells. The first term, mononuclear phagocyte system, refers to the group of cells consisting of macrophages, dendritic cells, and monocytes. The term reticuloendothelial system describes the cells that line the sinusoids of the liver and spleen, which are responsible for phagocytizing bacteria, cellular debris, and foreign bodies. Finally, myeloid-derived suppressor cells are a type of immune cell that can inhibit the immune response against tumor cells and chronic infections. Understanding the different synonyms for "system of macrophages" helps to widen the scope of research on these important immune cells.