Neutrophil: Difference between revisions
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| author = American Proficiency Institute}}</ref> | | author = American Proficiency Institute}}</ref> | ||
==Polymorphonuclear neutrophil== | ==Polymorphonuclear neutrophil== | ||
The mature form of '''polymorphonuclear neutrophil (PMN)''' has a nucleus with three to five lobes connected by slender threads of [[chromatin]]. | The mature form of '''polymorphonuclear neutrophil (PMN)''' has a nucleus with three to five lobes connected by slender threads of [[chromatin]]. The average mature neutrophil has a diameter of about 13-15µm and a granulated cytoplasm. | ||
== Chemotaxis and migration == | |||
The neutrophil is able to chemotactically migrate to infected tissue, moving upstream against a concentration gradient of Interleukin-6, <ref name=Kierszchenbaum>{{citation | |||
| title = Histology and cell biology | |||
| year = 2006 | |||
| author = Dr. Abraham L. Kierszchenbaum}}</ref> secreted by activated [[epithelium|endothelial cells]], [[mast cell]]s and [[macrophage]]s. When nearing the site of infection, the neutrophil will attach repeatedly to the endothelial blood vessel lining viz. selectins, thus dissipating kinetic energy. When the neutrophil has been slowed down enough, it will migrate from the blood vessel lumen to the infected tissue via an [[integrin]]-mediated pathway. | |||
== Activation == | |||
Because of its relative abundance compared to other leukocytes, neutrophil granulocytes are often the first to arrive at sites of new infection. The neutrophil granulocyte is activated through recognition of target molecules. The neutrophil granulocyte expresses many different surface receptors, some of which bind molecules that are unique to pathogens<ref name=FGH>{{citation | |||
| title = Histology - textbook and atlas | |||
| year = 2007 | |||
| author = Finn Geneser}}</ref> such as [[peptidoglycan]], a component of bacterial cell walls. Apart from the innate ability to recognize potential pathogens, the neutrophil is also able to be activated by target-bound opsonins ([[antibody|antibodies]]), thus making the neutrophil a humoral effector cell. | |||
== Phagocytosis and lysis == | |||
The neutrophil granulocyte is a professional [[phagocyte]], capable of ingesting and [[lysis|lysing]] pathogens. | |||
=== The respiratory burst === | |||
The neutrophil's lytic pathway involves an oxidative burst, in which massive amounts of oxidants are synthesized and released onto the ingested pathogen | |||
==References== | ==References== | ||
{{reflist|2}} | {{reflist|2}} | ||
Revision as of 15:25, 30 December 2009
A neutrophil is a granular, nucleated leukocyte , and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes.[1] They are quick to respond to infection challenge, often within hours. They are ephemeral cells, with a half-life on the order of 6 hours.[2] Neutrophils are more associated with acute inflammatory response than macrophages, which are more involved in chronic inflammation. [3] They normally make up 40% to 60% percent of all white cells; there may be an additional 0 to 3 percent of immature band neutrophils. [4]
While their role has clasically been associated with phagocytosis, a means of cell-mediated immune response in which they are attracted to targets via chemokines, more and more information has been accumulated about their role in releasing cytokines, especially interleukin 12 (IL-12). IL-12 encourages the production of [[interferon#interferon-gamma|interferon gamma (γ-interferon). [5]
Precursors
In the creation of white cells, the original progenitor is the pluripotent stem cell. Under the influence of interleukins IL-1, IL-3, and IL-6, they form committed stem cells (i.e., progenitors). The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) causes differentiation into the neutrophils, with maturation to polymorphonuclear neutrophils via juvenile and band forms.
Immature forms of neutrophil are juvenile and band. Band neutrophils are immature cells, released by the bone marrow in response to demand. They have a single nucleus resembling a band, a sausage, or the letters C or U. [6]
Polymorphonuclear neutrophil
The mature form of polymorphonuclear neutrophil (PMN) has a nucleus with three to five lobes connected by slender threads of chromatin. The average mature neutrophil has a diameter of about 13-15µm and a granulated cytoplasm.
Chemotaxis and migration
The neutrophil is able to chemotactically migrate to infected tissue, moving upstream against a concentration gradient of Interleukin-6, [7] secreted by activated endothelial cells, mast cells and macrophages. When nearing the site of infection, the neutrophil will attach repeatedly to the endothelial blood vessel lining viz. selectins, thus dissipating kinetic energy. When the neutrophil has been slowed down enough, it will migrate from the blood vessel lumen to the infected tissue via an integrin-mediated pathway.
Activation
Because of its relative abundance compared to other leukocytes, neutrophil granulocytes are often the first to arrive at sites of new infection. The neutrophil granulocyte is activated through recognition of target molecules. The neutrophil granulocyte expresses many different surface receptors, some of which bind molecules that are unique to pathogens[8] such as peptidoglycan, a component of bacterial cell walls. Apart from the innate ability to recognize potential pathogens, the neutrophil is also able to be activated by target-bound opsonins (antibodies), thus making the neutrophil a humoral effector cell.
Phagocytosis and lysis
The neutrophil granulocyte is a professional phagocyte, capable of ingesting and lysing pathogens.
The respiratory burst
The neutrophil's lytic pathway involves an oxidative burst, in which massive amounts of oxidants are synthesized and released onto the ingested pathogen
References
- ↑ National Library of Medicine, Medical Subject Headings (MeSH)
- ↑ Ganong, William F. (Nineteenth edition, 1999), Review of Medical Physiology, Appleton & Lange,pp. 494-496
- ↑ , Phagocytosis, Conjoint 401-403, University of Washington
- ↑ "Complete Blood Count", MedLine Plus
- ↑ Denkers EY, Del Rio L, Bennouna S (2003), Neutrophil production of IL-12 and other cytokines during microbial infection, in Cassatella, Marco A., "The Neutrophil: An Emerging Regulator of Inflammatory and Immune Response", Chem Immunol Allergy
- ↑ American Proficiency Institute (2004), Educational Commentary -- Blood Cell Identification
- ↑ Dr. Abraham L. Kierszchenbaum (2006), Histology and cell biology
- ↑ Finn Geneser (2007), Histology - textbook and atlas