Phagocyte
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217492014
2008-06-06T07:55:06Z
EmreDuran
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A '''phagocyte''' is a [[biological cell]] that ingests and destroys foreign matter such as [[microorganism]]s and debris by a process called [[phagocytosis]]. The term means "cell eater" in [[Greek language|Greek]].
== Types ==
There are three main categories of phagocytes: <ref>{{eMedicineDictionary|Phagocyte}}</ref>
* [[macrophage]]s (and [[monocyte]]s)
* microphages, such as [[Granulocyte|polymorphonuclear leukocytes]] (primarily [[neutrophil granulocyte|neutrophils]])
* dendritic cells
== Functions ==
Phagocytes eat pathogens and are extremely useful as an initial [[immune system]] response to [[infection]]. They contain many [[lysosomes]] that enable them to digest foreign material. They engulf [[pathogen]]s, debris, dead or dying cells and [[extracellular matrix]]. After engulfment into a [[phagosome]], a [[lysosome]] which is filled with digestive enzymes ([[protease]]s and [[oxygen radical]]s) fuses with it to form the [[phagolysosome]] in which the phagocytosed material is digested.
If the [[skin]] is broken, the first type of phagocyte that migrate to sites of injury are neutrophils. They fight [[bacteria]] by releasing [[cytotoxicity|cytotoxic]] granules and by phagocytosis. Phagocytosis is an active process in [[wound]] [[healing]].
In pathogen phagocytosis, specialised [[antigen-presenting cells]] ([[B cells]], [[dendritic cells]] and [[macrophages]]) present on their surfaces small [[peptide]]s that resulted from the digestion, bound to [[MHC class II]] [[molecule]]s. [[Helper T cells]] (CD4+) later recognize these [[antigens]] complemented with a second signal, and supplement the cell-mediated immune response.
Phagocytes can also induce [[apoptosis]] of normal and [[tumor cell]]s, produce [[cationic]] proteins, [[complement]] components and [[clotting]] factors, [[arachidonic acid]] metabolites, [[prostaglandin]]s, [[leukotriene]]s, [[thromboxane]]s, [[cytokine]]s, proteases and [[hydrolase]]s, reactive oxygen and [[nitrogen]] intermediates.
== Resistance by pathogen ==
Many pathogens can delay or prevent the creation of the phagolysosome such as ''[[Mycobacterium tuberculosis]]'', ''[[Salmonella typhi]]'' and ''[[Legionella]]''. Others, such as the [[parasite]]s of the genus ''[[Leishmania]]'', able to resist or circumvent being digested in the phagolysosome.
One function of T-helper cells is to activate phagocytes to digest intracellular pathogens.
== Etymology ==
The word ''phagocyte'' means "cell that eats", and originates from the Greek words ''phagein'', meaning 'eat', and ''kytos'', meaning 'hollow'.
== References ==
<references/>
== External links ==
* {{MeshName|Phagocytes}}
{{Blood}}
{{Immune_system}}
[[Category:Leukocytes]]
{{immunology-stub}}
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