Granulocyte
| Granulocyte | |
|---|---|
 A basophilic granulocyte. | |
| Details | |
| System | Immune system |
| Identifiers | |
| MeSH | D006098 |
| FMA | 62854 |
| Anatomical terms of microanatomy | |
Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm.[1] Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear, that is, they have varying shapes (morphology) of the nucleus (segmented, irregular; often lobed into three segments); and are referred to as polymorphonuclear leukocytes (PMN, PML, or PMNL). In common terms, polymorphonuclear granulocyte refers specifically to "neutrophil granulocytes",[2] the most abundant of the granulocytes; the other types (eosinophils, basophils, and mast cells) have varying morphology. Granulocytes are produced via granulopoiesis in the bone marrow.
Types
There are four types of granulocytes (full name polymorphonuclear granulocytes):[3]
Except for the mast cells, their names are derived from their
Neutrophils
Neutrophils are normally found in the bloodstream and are the most abundant type of phagocyte, constituting 60% to 65% of the total circulating white blood cells,[4] and consisting of two subpopulations: neutrophil-killers and neutrophil-cagers. One litre of human blood contains about five billion (5x109) neutrophils,[5] which are about 12–15 micrometres in diameter.[6] Once neutrophils have received the appropriate signals, it takes them about thirty minutes to leave the blood and reach the site of an infection.[7] Neutrophils do not return to the blood; they turn into pus cells and die.[7] Mature neutrophils are smaller than monocytes, and have a segmented nucleus with several sections(two to five segments); each section is connected by chromatin filaments. Neutrophils do not normally exit the bone marrow until maturity, but during an infection neutrophil precursors called myelocytes and promyelocytes are released.[8]
Neutrophils have three strategies for directly attacking micro-organisms: phagocytosis (ingestion), release of soluble anti-microbials (including granule proteins), and generation of neutrophil extracellular traps (NETs).[9] Neutrophils are professional
Neutrophils have two types of granules; primary (azurophilic) granules (found in young cells) and
Eosinophils
Eosinophils also have kidney-shaped
Basophils
Basophils are one of the least abundant cells in
When an infection occurs, mature basophils will be released from the bone marrow and travel to the site of infection.
Mast cells
Mast cells are a type of granulocyte that are present in tissues;
Development
Granulocytes are derived from stem cells residing in the bone marrow. The differentiation of these stem cells from multipotent hematopoietic stem cell into granulocytes is termed granulopoiesis. Multiple intermediate cell types exist in this differentiation process, including myeloblasts and promyelocytes.[citation needed]
Function
Granule contents
Examples of toxic materials produced or released by degranulation by granulocytes on the ingestion of microorganisms are:
- Antimicrobial agents (Defensins and Eosinophil cationic protein)
- Enzymes
- Lysozyme: dissolves cell walls of some gram-positive bacteria
- Acid hydrolases: further digest bacteria
- Low pH vesicles(3.5-4.0)
- Toxic nitrogen oxides (nitric oxide)
- Toxic hydroxy radicals, singlet oxygen, hypohalite)
Clinical significance
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
There is usually a granulocyte
Research suggests giving granulocyte transfusions to prevent infections decreased the number of people who had a bacterial or fungal infection in the blood.[25] Further research suggests participants receiving therapeutic granulocyte transfusions show no difference in clinical reversal of concurrent infection.[26]
Additional images
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Hematopoiesis
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See also
References
- ISBN 978-0-544-18897-6.
- ISBN 978-0-544-18897-6.
- ^ PMID 28642280.
- ISBN 80-967366-1-2. Archived from the originalon December 31, 2010. Retrieved March 28, 2009.
- ^ Hoffbrand p. 331
- ^ Abbas, Chapter 12, 5th Edition[full citation needed][page needed]
- ^ a b Sompayrac p. 18
- PMID 9853933.
- S2CID 8068543.
- ^ Robinson p. 187 and Ernst pp. 7–10
- ^ Paoletti p. 62
- PMID 17991288.
- ^ a b c Mayer, Gene (2006). "Immunology — Chapter One: Innate (non-specific) Immunity". Microbiology and Immunology On-Line Textbook. USC School of Medicine. Retrieved November 12, 2008.
- PMID 18787642.
- S2CID 22372863.
- ^ a b Hess CE. "Segmented Eosinophil". University of Virginia Health System. Archived from the original on 2009-08-13. Retrieved 2009-04-10.
- ^ ISBN 978-0-9631172-1-2.
- PMID 20176269.
- ^ a b Campbell p. 903
- PMID 18727793.
- PMID 16612762.
- ^ Hess CE. "Mature Basophil". University of Virginia Health System. Archived from the original on 2009-08-13. Retrieved 2009-04-10.
- S2CID 38504601.
- PMID 26377554.
MCs originate from a bone marrow progenitor and subsequently develop different phenotype characteristics locally in tissues. Their range of functions is wide and includes participation in allergic reactions, innate and adaptive immunity, inflammation, and autoimmunity [34]. In the human brain, MCs can be located in various areas, such as the pituitary stalk, the pineal gland, the area postrema, the choroid plexus, thalamus, hypothalamus, and the median eminence [35]. In the meninges, they are found within the dural layer in association with vessels and terminals of meningeal nociceptors [36]. MCs have a distinct feature compared to other hematopoietic cells in that they reside in the brain [37]. MCs contain numerous granules and secrete an abundance of prestored mediators such as corticotropin-releasing hormone (CRH), neurotensin (NT), substance P (SP), tryptase, chymase, vasoactive intestinal peptide (VIP), vascular endothelial growth factor (VEGF), TNF, prostaglandins, leukotrienes, and varieties of chemokines and cytokines some of which are known to disrupt the integrity of the blood-brain barrier (BBB) [38–40].
They key role of MCs in inflammation [34] and in the disruption of the BBB [41–43] suggests areas of importance for novel therapy research. Increasing evidence also indicates that MCs participate in neuroinflammation directly [44–46] and through microglia stimulation [47], contributing to the pathogenesis of such conditions such as headaches, [48] autism [49], and chronic fatigue syndrome [50]. In fact, a recent review indicated that peripheral inflammatory stimuli can cause microglia activation [51], thus possibly involving MCs outside the brain. - PMID 26118415.
- PMID 27128488.
Bibliography
- Campbell NA, Reece JB (2002). Biology (6th ed.). Pearson Education, Inc. ISBN 978-0-8053-6624-2.
- Delves PJ, Martin SJ, Burton DR, Roit IM (2006). Roitt's Essential Immunology (11th ed.). Blackwell Publishing. ISBN 978-1-4051-3603-7.
- Ernst JD, Stendahl O (2006). Phagocytosis of Bacteria and Bacterial Pathogenicity. Cambridge University Press. ISBN 0-521-84569-6.
- Hoffbrand AV, Pettit JE, Moss PA (2005). Essential Haematology (4th ed.). Blackwell Science. ISBN 978-0-632-05153-3.
- Paoletti R, Notario A, Ricevuti G, eds. (1997). Phagocytes: Biology, Physiology, Pathology, and Pharmacotherapeutics. The New York Academy of Sciences. ISBN 978-1-57331-102-1.
- Robinson JP, Babcock GF, eds. (1998). Phagocyte Function —A guide for research and clinical evaluation. Wiley–Liss. ISBN 978-0-471-12364-4.
- Sompayrac L (2008). How the Immune System Works (3rd ed.). Blackwell Publishing. ISBN 978-1-4051-6221-0.
External links
Media related to Granulozyt at Wikimedia Commons
