Neutrophils (also known as neutrocytes ) are the most abundant and most abundant types of granulocytes (40% to 70%) types of white blood cells in most mammals. They form an important part of the innate immune system. Their function varies in different animals.
They are formed from stem cells in the bone marrow and are subdivided into sub-populations of neutrophil-killers and neutrophil-cagers. They are short-lived and very moving, or moving, because they can enter parts of the tissue where other cells/molecules can not. Neutrophils can be divided into segmented neutrophils and neutrophil bands (or bands). They form part of the polymorphonuclear cells family (PMN) together with basophils and eosinophils.
The name neutrophil is derived from the characteristic staining on hematoxylin and histological (H & amp; E) eosin or cytological preparations. Whereas white basophilic white blood cells are dark blue stains and eosinophilic white blood cells are bright red, neutrophils stain neutral pink. Typically, neutrophils contain a nucleus that is divided into 2-5 lobes.
Neutrophils are a type of phagocytes and are usually found in the bloodstream. During the initial (acute) phase of inflammation, mainly as a result of bacterial infection, environmental exposure, and some cancers, neutrophils are among the first responders of inflammatory cells to migrate in the direction of inflammation. They migrate through the blood vessels, then through the interstitial tissues, following chemical signals such as Interleukin-8 (IL-8), C5a, fMLP, Leukotriene B4 and H 2 O 2 in a process called chemotaxis. They are the dominant cells in the pus, explaining the appearance of the white/yellowish.
Neutrophils are recruited to the site of injury within minutes of trauma and are characteristic of acute inflammation; However, as some pathogens become indigestible, they can not resolve a particular infection without the help of other types of immune cells.
Video Neutrophil
Structure
When attached to the surface, neutrophil granulocytes have an average diameter of 12-15 micrometers (Âμm) in peripheral blood smear. In suspension, human neutrophils have an average diameter of 8.85 Ã,Âμm.
With eosinophils and basophils, they form a class of polymorphonuclear cells, named for the nuclear multilobulus form (compared with lymphocytes and monocytes, other types of white blood cells). The nucleus has a distinctive lobe appearance, a separate lobe connected by chromatin. Nucleolus disappears when neutrophils mature, which is something that occurs only in some nucleated cell types. In the cytoplasm, small Golgi apparatus, mitochondria and ribosomes are sparse, and rough endoplasmic reticulum does not exist. The cytoplasm also contains about 200 grains, of which one third is azurophilic.
Neutrophils are sexually dimorphic. Neutrophils from females show a small additional X chromosome structure, known as a "neutrophil drumstick".
Neutrophils will show increased segmentation (many core segments) as they mature. Normal neutrophils should have 3-5 segments. Hypersegmentation is not normal but occurs in some disorders, especially vitamin B deficiency 12 . This is recorded in manual reviews of blood tests and is positive when most or all neutrophils have 5 or more segments.
Neutrophils are the most abundant white blood cells in humans (about 10 11 are produced daily); they account for about 50-70% of all white blood cells (leukocytes). The normal range expressed for human blood counts varies between laboratories, but the number of neutrophils 2.5-7.5 x 10 9 /L is the standard normal range. People of African and Middle Eastern descent may have lower numbers, which are still normal. A report can divide neutrophils into neutrophils and segmented bands.
When circulating in the bloodstream and inactive, neutrophils are spherical. Once activated, they change shape and become more amorphous or amoeble-like and can extend pseudopods as they hunt for antigens.
Neutrophils have a preference for ingestion of refined carbohydrates (from digested glucose, fructose, sucrose, honey and orange juice) over the bacteria. In 1973 Sanchez et al. found that the neutrophil phagocytic capacity to swallow bacteria is affected when simple sugars are digested, and the fasting strengthens the phagocytic capacity of neutrophils to ingest bacteria. However, normal starch digestion has no effect. It was concluded that the function, and not the amount, of phagocytes in the swallowing bacteria was changed by sugar consumption. In 2007 researchers at the Whitehead Institute of Biomedical Research found that given a choice of sugar, neutrophils ingested some types of sugars in a special way.
Maps Neutrophil
Development
Life span
The mean age of neutrophils inactive in the circulation has been reported by different approaches between 5 and 90 hours. After activation, they marginalize (position themselves adjacent to the vascular endothelium) and undergo retrieval depending on the selectivity followed by integrin-dependent attachment in many cases, after which they migrate to tissue, where they persist for 1-2 days.
Neutrophils are much more than long-lived monocyte/macrophage phagocytes. Pathogens (disease-causing microorganisms or viruses) are likely to first find neutrophils. Some scholars hypothesize that the short life span of neutrophils is an evolutionary adaptation. The short life span of neutrophils minimizes the propagation of pathogens that parasitize phagocytes because the more time a parasite spends outside the host cell, the more likely they will be destroyed by some of the body's defense components. Also, since neutrophil antimicrobial products can also damage the host tissue, their short lifespan limits damage to the host during inflammation.
Neutrophils are removed after pathogenic phagocytosis by macrophages. PECAM-1 and phosphatidylserine on the cell surface are involved in this process.
Function
Chemotaxis
Neutrophils undergo a process called chemotaxis through the amoeboid movement, which allows them to migrate to infectious sites or inflammation. Cell surface receptors allow neutrophils to detect chemical gradients from molecules such as interleukin-8 (IL-8), gamma interferon (IFN-?), C3a, C5a, and Leukotriene B4, which these cells use to direct their migratory pathways.
Neutrophils have a variety of specific receptors, including those for complement, cytokines such as interleukin and IFN-, chemokines, lectins, and other proteins. They also express receptors to detect and adhere to endothelium and Fc receptors for opsonin.
In leukocytes that respond to chemotherapy, cellular polarity is governed by the activity of Rho guanosine triphosphate (Rho GTPases) and phosphoinositide 3-kinase (PI3Ks). In neutrophils, PI3Ks lipid products regulate Rho GTPases activation and are necessary for cell motility. They accumulate asymmetrically to the plasma membrane at the polarization edge of polarized cells. Spatially regulating Rho GTPases and regulating the leading edge of cells, PI3K and their lipid products can play an important role in determining the polarity of leukocytes, as compass molecules that tell the cell where it crawls.
It has been shown in mice that under certain conditions neutrophils have a specific type of migratory behavior called clustered neutrophils in which they migrate in a highly coordinated and accumulated way and clustered to inflammatory sites.
Anti-microbial function
Being so muscular, neutrophils rapidly converge on the focus of infection, attracted by cytokines expressed by active endothelium, mast cells, and macrophages. Neutrophils express and release cytokines, which in turn reinforce the inflammatory reaction by several other cell types.
In addition to recruiting and activating other cells of the immune system, neutrophils play a key role in front line defense against pathogen invasion. Neutrophils have three methods for directly attacking micro-organisms: phagocytosis (consumption), degranulation (dissolved anti-microbial release), and generation of neutrophil extracellular traps (NETs).
Phagocytosis
Neutrophils are phagocytes, which are capable of ingesting microorganisms or particles. In order for targets to be recognized, they must be coated opsonin - a process known as opsonizing antibodies. They can internalize and kill many microbes, each phagocytic event results in the formation of phagosomes in which reactive oxygen species and hydrolytic enzymes are secreted. Oxygen consumption during the formation of reactive oxygen species has been called "respiratory blast", although it is not associated with respiration or energy production.
Respiratory bursts involve activation of NADPH oxidase enzyme, which produces large amounts of superoxide, reactive oxygen species. Superoxide decays spontaneously or is broken down by an enzyme known as superoxide dismutase (Cu/ZnSOD and MnSOD), into hydrogen peroxide, which is then converted to hypochlorite acid (HClO), by the green heme enzyme myeloperoxidase. It is thought that the bactericidal properties of HClO are sufficient to kill phagocytosed bacteria by neutrophils, but this can instead be a necessary step for the activation of proteases.
Degranulation
Neutrophils also release various proteins in three types of granules by a process called degranulation. The contents of these granules have antimicrobial properties, and help fight infection.
Neutrophil extracellular traps
In 2004, Brinkmann and colleagues described a striking observation that neutrophil activation led to the release of web-like DNA structures; this is the third mechanism for killing bacteria. This neutrophil extracellular trap (NET) consists of a fiber network consisting of chromatin and serine proteases that capture and kill extracellular microbes. It is recommended that NET provides high local concentrations of antimicrobial components and bind, disarm, and kill microbes independently of phagocytic uptake. In addition to their possible antimicrobial properties, NET can serve as a physical barrier that prevents further spread of pathogens. Bacterial traps can be a very important role for NET in sepsis, where NET is formed in blood vessels. More recently, NET has been shown to play a role in inflammatory diseases, as NET can be detected in preeclampsia, a pregnancy-related inflammatory disorder in which neutrophils are known to be activated. In addition, NET is known to exhibit both pro-thrombotic effects in vitro and in vivo.
Clinical interests
The low neutrophil count is called neutropenia . It can be congenital (developing at or before birth) or may develop later, as in the case of aplastic anemia or some type of leukemia. It can also be a drug side effect, the most obvious chemotherapy. Neutropenia makes a person very susceptible to infection. It can also be the result of colonization by intracellular neutrophilic parasites.
In alpha 1-antitrypsin deficiency, important elastase neutrophil enzymes are inadequately inhibited by alpha 1-antitrypsin, causing excessive tissue damage in the presence of inflammation - the most prominent being pulmonary emphysema. The negative effects of elastase have also been shown in cases when neutrophils are activated excessively (in healthy individuals) and release enzymes in the extracellular space. Unregulated activity of elastase neutrophils can cause lung barrier disorders that exhibit symptoms associated with acute lung injury. Enzymes also affect macrophage activity by splitting their toll-like receptors (TLRs) and decreasing regulation of cytokine expression by inhibiting nuclear translocation of NF-? B.
In Familial Mediterranean fever (MFF), mutations in the pyrin (or marenostrine ) genes, expressed primarily in neutrophil granulocytes, lead to an acutely active constitutive phase response. and cause fever, arthralgia, peritonitis, and - finally - amyloidosis.
Decreased neutrophil function has been associated with hyperglycemia. Dysfunction in the biochemical pathway of myeloperoxidase neutrophils and decreased degranulation is associated with hyperglycemia.
Absolute Neutrophil count (ANC) is also used in diagnosis and prognosis. ANC is a gold standard for determining the severity of neutropenia, and thus a neutropenic fever. ANC & lt; Cell <3> is considered neutropenia, but & lt; 500 <3> is considered heavy. There is also new research that binds ANC to myocardial infarction as an aid in early diagnosis.
Neutrophil Antigen
There are five (HNA 1-5) sets of recognized neutrophil antigens. The three HNA-1 antigens (a-c) lie in the low affinity Fc-? receptor IIIb (FCGR3B: CD16b) The known single HNA-2A antigen is located on CD177. The HNA-3 antigen system has two antigens (3a and 3b) located on the seventh exon of the CLT2 gene (SLC44A2). The HNA-4 and HNA-5 antigen systems each have two known antigens (a and b) and are located in integrin 2 2. The HNA-4 is located on the M chain (CD11b) and HNA-5 is located in the integrin L unit (CD11a ).
Subpopulation
Two functionally identifiable neutrophil subpopulations were identified based on different levels of reactive oxygen generation generation, membrane permeability, enzyme system activity, and ability to be inactivated. Cells of a subpopulation with high membrane permeability (neutrophil-killers) intensively produce reactive and inactive oxygen metabolites as a result of interaction with the substrate, while other neutrophil-cagers produce less intensive reactive oxygen species, disobey substrate and preserve their activity.
Video
[1] Neutrophils display highly directed amoeboid motility in the infected footpads and phalanxes. Intravital imaging was performed in the path of the LysM-eGFP rat footpad 20 min after infection with Listeria monocytogenes .
Additional images
References
External links
- Neutropenia Information
- Absolute Neutrophil Count Calculator
- Fill in Elements and Distributions of Neutrophil Elements
Source of the article : Wikipedia
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