Mononuclear Phagocyte System Definition and Function

The combined activity of the immune system’s phagocytes-monocytes in the blood circulation and macrophages in the tissues-to consume cellular debris.

These cells are scavengers within the body, responsible for cleaning up after B-cell lymphocytes, T-cell lymphocytes, and natural killer (NK) cells. They also clear the debris that results from normal cell death (apoptosis). They are called mononuclear because their cell structure contains a single nucleus; neutrophils, which are also phagocytes, have multiple nuclei (and are called polymorphonuclear).

The complement cascade (an interaction of proteins or factors that begins with antibodyantigen binding) is the primary alert mechanism that activates the mononuclear phagocyte system. Monocytes and macrophages work in a coordinated fashion, communicating via cytokines (cell-originated biochemical messages) with other cells involved in the immune response.

For further discussion of the mononuclear phagocyte system within the context of the structures and functions of the immune system, please see the overview section “The Immune System and Allergies.”

See also B-CELL LYMPHOCYTECELL STRUCTURE AND FUNCTION; GENEGRANULOCYTEMACROPHAGEMONOCYTENATURAL KILLER (NK) CELL; PHAGOCYTEPHAGOCYTOSIST-CELL LYMPHOCYTE.

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