Monocytes (Monos, Mo, AMC)
Monocytes are the largest of all leukocytes. They are agranular. Monocytes are produced in the bone marrow which they leave entering the bloodstream being not fully mature cells. These immature cells have the greatest phagocytic ability (they ingest harmful foreign particles, bacteria, and dead or dying cells). Monocytes circulate in the bloodstream for a few days and then migrate into the tissues where they change into macrophages which, along with neutrophils, kill foreign, pathogenic microorganisms. However, macrophages are bigger and live longer than neutrophils.
High monocyte counts (monocytosis) often occur due to infectious diseases. An increased count of monocytes may be found during the recovery period after severe infections, also may be an indicator of infectious mononucleosis, a very common viral infection.
A low count of monocytes (monocytopenia) or lack of monocytes in the peripheral blood may develop due to severe pyoinflammatory and infectious diseases. Also, it may be caused by the depressed function of the bone marrow due to bone marrow failure (aplastic anemia, vitamin B12 deficiency anemia).