Thursday
12Nov2009
Saturday
19Aug2006
Neutrophil granulocytes..
Saturday, August 19, 2006 at 04:00PM are attracted to wounds and kill almost every bacterium they want. They are fast, granular, flexible, metabolically active and very powerful.
Neutrophils are the most common type of white blood cells and form an integral part of the innate immune system. These phagocytes stem from the hematopoietic bone marrow (~90%) and are found in the blood stream (~10%) with a life time about 6 to 8 hours, but not in lymphatic organs like lymph nodes. Having neutrally-staining cytoplasmic granules their name derives from their staining characteristics. However CD32 and CD68 are the signature cell surface markers. Neutrophil have an average volume of 330 femtoliters and a diameter of 12-15 micrometers. Together with the eosinophil and the basophil they form the class of polymorphonuclear cells(PMNs), as their nucleus has a characteristic, multilobulated shape. As the most abundant leukocytes, neutrophils account for 70% of all white blood cells counting 2.5-7.5 x106/ml as standard range.
Attracted by cytokines as well as other mediators like cortison or adrenalin, neutrophils plays a key role during inflammatory reactions. Upon activation, they adjacent selectin and integrin dependent to the blood vessel endothelium and undergo migrate into tissues, where they survive for 1-2 days. Dead and living neutrophils are part of pus. As active phagocytes, they are capable of ingesting microorganisms like bacteria or fungis like candida albicans. The antibody dependent, antigen specific phygocytosis as well as the unspecific uptake of the microbes results in their capture in lysosomes. Beside of superoxids, alkalic phosphatases, myeloperoxidase, lactoferrrin, collagenases and elastase are the main substance of such lysosomes to kill and clean up such microbes and to modulate the tissue during inflammation. However, neutrophils can only execute one phagocytic event, expending all of their glucose reserves in an vigorous respiratory burst.This burst involves the activation of an NADPH oxidase enzyme, which produces superoxide to kill the ingested organism. But neutrophil antimicrobial products can also damage host tissues, and the short life could probably be an evolutionary adaptation to limit damage to the host.
In contrast predispose low neutrophil counts heavily for infections. The term is Neutropenia. This can be congenital or it can develop later, for example as in aplastic anemia or some kinds of leukemia. It can also be a side-effect of medication, most prominently caused by chemotherapy. Hereditary functional disorders of neutrophils lead to deficiencies in phagocytosis or in the respiratory burst.
Finally cause a leaky control of neutrophil activation products to excessive tissue damage in the presence of inflammation – most prominently in pulmonary emphysemia. In Familial Mediterranean fever (FMF), a mutation in the pyrin gene, which is expressed mainly in neutrophil granulocytes, leads to a constitutionally active acute phase response and causing attacks of fever, arthralgia, peritonitis and - eventually - amyloidosis
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