Monocytes: Large, phagocytic mononuclear leukocytes produced in the vertebrate BONE MARROW and released into the BLOOD; contain a large, oval or somewhat indented nucleus surrounded by voluminous cytoplasm and numerous organelles.

monocytes: Monocytes are essentially immature macrophages. After their formation and release by the bone marrow, these cells enter the bloodstream and circulate for about 36 hours while they mature into macrophages. Sessile macrophages are the tissue counterparts of monocytes of peripheral blood. Sometimes, the term histiocytes is used for these cells. Monocytes together with polymorphonuclear leukocytes (granulocytes) are being referred to collectively as myelomonocytic cells. The term plasmacytoid monocytes refers to a population of cells known also asT-associated plasma cells, plasmacytoid T-cells, plasmacytoid predendritic cells, plasmacytoid dendritic cells, or natural IFN-producing cells. See also: dendritic cells.

monocytes: One of three types of white blood cells. Monocytes are precursors to macrophages.