macrophage mac·ro·phage (māk'rə-fāj')
Any of the large phagocytic cells found in the reticuloendothelial system.
Any of various large white blood cells that play an essential immunologic role in vertebrates and some lower organisms by eliminating cellular debris and particulate antigens, including bacteria, through phagocytosis. Macrophages develop from circulating monocytes that migrate from the blood into tissues throughout the body, especially the spleen, liver, lymph nodes, lungs, brain, and connective tissue. Macrophages also participate in the immune response by producing and responding to inflammatory cytokines.