Granulocytes are a category of
white blood cells characterised by the presence of granules in their cytoplasm. [eMedicineDictionary|granulocyte] They are also called polymorphonuclear leukocytes (PMN or PML) because of the varying shapes of the nucleus, which is usually lobed into three segments. In common parlance, the term "polymorphonuclear leukocyte" often refers specifically to neutrophil granulocytes, [eMedicineDictionary|polymorphonuclear+leukocyte] the most abundant of the granulocytes. Granulocytes or PMN are released from the bone marrow by the regulatory complement proteins.
There are three types of granulocytes, distinguished by their appearance under
Their names are derived from their staining characteristics; for example, the most abundant granulocyte is the
neutrophil granulocyte, which has neutrally-staining cytoplasmic granules.
Other white blood cells which are not granulocytes ("
agranulocytes") are mainly lymphocytes and monocytes.
Toxic materials produced or released
Examples of toxic materials produced or released by
degranulationby granulocytes on the ingestion of microorganism includes:
* Low pH vesicles (3.5-4.0)
oxygen-derived products (e.g. superoxide, hydrogen peroxide, hydroxyradicals, singlet oxygen, hypohalite)
nitrogenoxides ( nitric oxide)
Antimicrobialagents ( Defensins and cationicproteins)
Lysozyme: dissolves cell walls of some gram positive bacteria
Acid hydrolases: further digest bacteria
Granulocytopenia is an abnormally low concentration of granulocytes in the blood. This condition reduces the body's resistance to many infections. Closely-related terms include
agranulocytosis(no granulocytes at all) and neutropenia(deficiency of neutrophil granulocytes). Transfusion of granulocytes would have been a solution to the problem. However, granulocytes live only ~10 hours in the circulation (for days in spleenor other tissue), which gives a very short-lasting effect. In addition, there are many complications of such procedure.
granulomais a tumorcontaining granulocytes, and a "granulomatosis" is a necrotizinggranuloma.
There is usually a granulocyte
chemotacticdefect in individuals who suffer from insulin dependent diabetes mellitus.
White blood cell
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