A large white blood cell with finely granulated chromatin dispersed throughout the nucleus that is formed in the bone marrow, enters the blood, and migrates into the connective tissue where it differentiates into a macrophage.

Part of the human body’s immune system.

Identified in stained smears by their large two-lobed nucleus.

Turn into macrophages and immune helper cells called dendritic cells.

Gradually replenish resident macrophages and dendritic cells under normal conditions.

Mobilize to infected tissue in response to inflammatory signals.

Half of all monocytes are stored as a reserve in the spleen the rest are circulating or in tissues.

Produced by the bone marrow from stem cell precursor monoblasts.

Circulate in the bloodstream for about one to three days and then migrate into tissues, and differentiate into macrophages or dendritic cells.

Monocytes are released into the circulation within 12-24 hours after their precursors have completed their last mitotic division.

Monocytesv do not have a large reserve of cells in a maturation storage pool as do granulocytes.

Monocytes in the circulation may be located in the circulating or marinating pool.

The ratio of circulating to marginating cells is 1:3.5.

Monocytes are estimated to have a circulatory half-life of about 8.5 hours, and the lifespan of tissue monocytes is variable but maybe live for months to years .

Account for three to eight percent of the leukocytes in the blood.

Macrophages protect tissues from foreign substances.

Macrophages possess a large smooth nucleus, large cytoplasm and many internal vesicles for processing foreign material.

Monocytes and their macrophage alteration allows phagocytosis.

Dendritic cell progeny provide antigen presentation and cytokine production.

Circulating monocytes are recruited by tumors and stromal cells through the release of chemokines and growth factors.
Monocytes at the tumor site are induced to differentiate with macrophages into tumor associated macrophages, acquiring pro tumor functions including cancer growth, angiogenesis, dissemination, matrix remodeling, and suppression of adaptive immune response.

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