What is "mononuclear phagocyte system"

n. a widely distributed system of free and fixed macrophages derived from bone marrow [syn: MPS, system of macrophages]

In immunology, the mononuclear phagocyte system or mononuclear phagocytic system (MPS) (also known as the reticuloendothelial system or macrophage system) is a part of the immune system that consists of the phagocytic cells located in reticular connective tissue. The cells are primarily monocytes and macrophages, and they accumulate in lymph nodes and the spleen. The Kupffer cells of the liver and tissue histiocytes are also part of the MPS. The mononuclear phagocyte system and the monocyte macrophage system refer to two different entities, often mistakenly understood as one.

"Reticuloendothelial system" is an older term for the mononuclear phagocyte system, but it is used less commonly now, as it is understood that most endothelial cells are not macrophages.