Monocytes Elevated

Monocytes are white blood cells that help other white blood cells to remove dead or damaged tissues, destroy cancer cells, and regulate immunity against foreign substances.

Monocytes are produced in the bone marrow and then enter the bloodstream, where they account for about 1 to 10% of the circulating leukocytes (200 to 600 monocytes per microliter of blood).  After a few hours they migrate to tissues such as the spleen, liver, lung, and bone marrow, where they mature into macrophages, the main scavenger cells of the immune system.

Causes and Development

An increased number of monocytes in the blood (monocytosis) occurs in response to chronic infections, in autoimmune disorders, in blood disorders, and in cancers.

Diagnosis and Tests

An increased percentage of monocytes may indicate:

• Chronic inflammatory disease
• Parasitic infection
• Tuberculosis
• Viral infection (for example, infectious mononucleosis, mumps, measles)