Tuesday, October 8, 2013

However, the various subsets may also be considered

However, the various subsets may also be considered part of the innate immune system where a restricted TCR or NK receptors may be used as a pattern recognition receptor. For example, according to this paradigm, large numbers of Vγ9/Vδ2 T cells respond within hours to common molecules produced by microbes, and highly restricted intraepithelial Vδ1 T cells will respond to stressed epithelial cells.HP Pavilion dv6-2115so laptop keyboard

The coagulation system overlaps with the immune system. Some products of the coagulation system can contribute to the non-specific defenses by their ability to increase vascular permeability and act as chemotactic agents for phagocytic cells. In addition, some of the products of the coagulation system are directlyantimicrobial. HP Pavilion dv6-2141ee laptop keyboard

For example, beta-lysine, a protein produced by platelets during coagulation, can cause lysis of many Gram-positive bacteria by acting as a cationic detergent.[4] Many acute-phase proteins of inflammation are involved in the coagulation system.

Also increased levels of lactoferrin and transferrin inhibit bacterial growth by binding iron, an essential nutrient for bacteria. HP Mini 210 laptop keyboard

The innate immune response to infectious and sterile injury is modulated by neural circuits that control cytokine production period. The Inflammatory Reflex is a prototypical neural circuit that controls cytokine production in spleen.[12] Action potentials transmitted via the vagus nerve to spleen mediate the release of acetylcholine, IBM Thinkpad R40 laptop keyboard

the neurotransmitter which inhibits cytokine release by interacting with alpha7 nicotinic acetylcholine receptors (CHRNA7) expressed on cytokine-producing cells.[13] The motor arc of the inflammatory reflex is termed the cholinergic anti-inflammatory pathway.

Cells of the innate immune system effectively prevent free growth of bacteria within the body; DELL Inspiron 6000 laptop keyboard

however, many pathogens have evolved mechanisms allowing them to evade the innate immune system.[15][16]

Evasion strategies that circumvent the innate immune system include intracellular replication, such as in Mycobacterium tuberculosis, or a protective capsule that prevents lysis by complement and by phagocytes, as in salmonella.[17] HP Pavilion dv6-2124eo laptop keyboard

 Bacteroides species are normally mutualistic bacteria, making up a substantial portion of the mammalian gastrointestinal flora.[18] Some species (B. fragilis, for example) are opportunistic pathogens, causing infections of the peritoneal cavity. These species evade the immune system through inhibition of phagocytosis HP Pavilion dv6-2173cl laptop keyboard

by affecting the receptors that phagocytes use to engulf bacteria or by mimicking host cells so that the immune system does not recognize them as foreign. Staphylococcus aureus inhibits the ability of the phagocyte to respond to chemokine signals. Other organisms such as M. tuberculosisLenovo ThinkPad Edge E525 laptop keyboard

Streptococcus pyogenes and Bacillus anthracis utilize mechanisms that directly kill the phagocyte.

Bacteria and fungi may also form complex biofilms, providing protection from the cells and proteins of the immune system; recent studies indicate that such biofilms are present in many successful infections, GATEWAY MX6956 laptop keyboard

including the chronic Pseudomonas aeruginosa and Burkholderia cenocepacia infections characteristic ofcystic fibrosis.

Antiviral host defense and creation of an effective antiviral state in a cell is essentially due to the role played by type I interferons (IFN) (Akira et al. 2006), mainly secreted by dendritic cells (DCs) (Le Bon and Tough, 2002). GATEWAY NX570X laptop keyboard

Viral components are recognized by different receptors: Toll-like receptor (TLR-3) are located in the endosomal membrane and recognizes double-stranded RNA (dsRNA), MDA5 and RIG-I are in the cytoplasm and recognize respectively long dsRNA and phosphate containing dsRNA (Baum and Garcia-Sastre, 2010). IBM Thinkpad Z60m laptop keyboard

The viral recognition by MDA5 and RIG-I in the cytoplasm induces a conformational change between the caspase-recruitment domain (CARD) and the CARD-containing adaptor MAVS. In parallel, the viral recognition by TLR-3 in the endocytic compartments induces the activation of the adaptor protein TRIF. ASUS X53S laptop keyboard

These two pathways converge in the recruitment and activation of the IKKε/TBK-1 complex, inducing phosphorylation and homo- and hetero-dimerization of transcription factors IRF3 and IRF7. These molecules are translocated in the nucleus, where they induce IFN production with the presence of C-Jun (transcription factor) and ATF-2 (activating transcription factor 2).  HP G71-445US laptop keyboard

Then, IFN bind to the IFN receptors and induce the expression of hundreds of interferon-stimulated genes (ISG) by the JAK/STAT pathway. These ISG produce proteins with antiviral properties, like protein kinase R (PKR) which inhibits viral protein synthesis, or the 2′,5′-oligoadenylate synthetase (OAS) family which degrade viral RNAm. Lenovo 3000 G530 4151 laptop keyboard

These molecules establish an effective antiviral state in the cell (Akira et al. 2006).

Some viruses are able to evade this immune system, by producing molecules that interfere with IFN production pathway. For example, the Influenza A virus NS1 protein binds single-stranded and/or dsRNA, inhibiting type I IFN production. TOSHIBA Mini NB 505-SP0160 Laptop Keyboard

Later in the defense reaction, this virus blocks PKR activation and the establishment of the antiviral state (Garcia-Sastre et al. 1998). The dengue virus (DENV) also inhibits type I IFN production by blocking IRF-3 phosophorylation using NS2B3 protease complex (Rodriguez-Madoz et al. 2010).  ACER Aspire 5610Z Laptop Keyboard

Bacteria (and perhaps other prokaryotic organisms), utilize a unique defense mechanism, called the restriction modification system to protect themselves from pathogens, such as bacteriophages. In this system, bacteria produce enzymes, called restriction endonucleases, that attack and destroy specific regions of the viral DNA of invading bacteriophages. COMPAQ Presario CQ60-201EP Laptop Keyboard

Methylation of the host's own DNA marks it as "self" and prevents it from being attacked by endonucleases.[20] Restriction endonucleases and the restriction modification system exist exclusively in prokaryotes.

Invertebrates do not possess lymphocytes or an antibody-based humoral immune system, SONY Vaio PCG-K23 Laptop Keyboard

and it is likely that a multicomponent, adaptive immune system arose with the first vertebrates.[21] Nevertheless, invertebrates possess mechanisms that appear to be precursors of these aspects of vertebrate immunity. Pattern recognition receptors are proteins used by nearly all organisms to identify molecules associated with microbial pathogens. SONY 147664712 Laptop Keyboard

Toll-like receptors are a major class of pattern recognition receptor, that exists in all coelomates (animals with a body-cavity), including humans.[22] The complement system, as discussed above, is a biochemical cascade of the immune system that helps clear pathogens from an organism, and exists in most forms of life. Some invertebrates, SONY Vaio PCG-K215S Laptop Keyboard

including various insects, crabs, and worms utilize a modified form of the complement response known as the prophenoloxidase (proPO) system.[21]

Antimicrobial peptides are an evolutionarily conserved component of the innate immune response found among all classes of life and represent the main form of invertebrate systemic immunity. TOSHIBA Satellite L775D-S7226 Laptop Keyboard

Several species of insect produce antimicrobial peptides known as defensins and cecropins.

In invertebrates, pattern recognition proteins (PRPs) trigger proteolytic cascades that degrade proteins and control many of the mechanisms of the innate immune system of invertebrates—including hemolymph coagulation and melanization.  HP G42-164LA Laptop Keyboard

Proteolytic cascades are important components of the invertebrate immune system because they are turned on more rapidly than other innate immune reactions because they do not rely on gene changes. Proteolytic cascades have been found to function the same in both vertebrate and invertebrates, even though different proteins are used throughout the cascades. Lenovo 04W0872 Laptop Keyboard

In the hemolymph, which makes up the fluid in the circulatory system of arthropods, a gel-like fluid surrounds pathogen invaders, similar to the way blood does in other animals. There are various different proteins and mechanisms that are involved in invertebrate clotting. In crustaceans, HP Envy 15 Laptop Keyboard

transglutaminase from blood cells and mobile plasma proteins make up the clotting system, where the transglutaminase polymerizes 210 kDa subunits of a plasma clotting protein. On the other hand, in the horseshoe crab species clotting system, components of proteolytic cascades are stored as inactive forms in granules of hemocytes, which are released when foreign molecules, GATEWAY NX570X Laptop Keyboard

like lipopolysaccharides enter.

Members of every class of pathogen which infect humans also infect plants. Although the exact pathogenic species vary with the infected species, bacteria, fungi, viruses, nematodes and insects can all cause plant disease. HP G61-336NR Laptop Keyboard

As with animals, plants attacked by insects or other pathogens use a set of complex metabolicresponses that lead to the formation of defensive chemical compounds that fight infection or make the plant less attractive to insects and other herbivores.[24](see: plant defense against herbivory). SONY VGN-FE31M Laptop Keyboard

Like invertebrates, plants neither generate antibody or T-cell responses nor possess mobile cells that detect and attack pathogens. In addition, in case of infection, parts of some plants are treated as disposable and replaceable, in ways that very few animals are able to do. Walling off or discarding a part of a plant helps stop spread of an infection.[24] ASUS X53S Laptop Keyboard

Most plant immune responses involve systemic chemical signals sent throughout a plant. Plants use pattern-recognition receptors to recognize conserved microbial signatures. This recognition triggers an immune response. The first plant receptors of conserved microbial signatures were identified in rice (XA21, 1995)[25][26] and in Arabidopsis (FLS2, 2000).[27] HP Pavilion DV7-3065dx Laptop Keyboard

 Plants also carry immune receptors that recognize highly variable pathogen effectors. These include the NBS-LRR class of proteins. When a part of a plant becomes infected with a microbial or viral pathogen, in case of an incompatible interaction triggered by specificelicitors, the plant produces a localized hypersensitive response (HR), HP 519265-001 Laptop Keyboard

in which cells at the site of infection undergo rapid programmed cell death to prevent the spread of the disease to other parts of the plant. HR has some similarities to animal pyroptosis, such as a requirement of caspase-1-like proteolytic activity of VPEγ, a cysteine protease that regulates cell disassembly during cell death.[28]  HP Compaq NW8440 Laptop Keyboard

"Resistance" (R) proteins, encoded by R genes, are widely present in plants and detect pathogens. These proteins contain domains similar to the NOD Like Receptors and Toll-like receptors utilized in animal innate immunity. Systemic acquired resistance (SAR) is a type of defensive response that renders the entire plant resistant to a broad spectrum of infectious agents.[29] DELL Vostro PP38L laptop keyboard

 SAR involves the production of chemical messengers, such as salicylic acid or jasmonic acid. Some of these travel through the plant and signal other cells to produce defensive compounds to protect uninfected parts, e.g., leaves.[30] Salicylic acid itself, although indispensable for expression of SAR, is not the translocated signal responsible for the systemic response.Lenovo Thinkpad X220 laptop keyboard

Recent evidence indicates a role for jasmonates in transmission of the signal to distal portions of the plant. RNA silencing mechanisms are also important in the plant systemic response, as they can block virus replication.[31] HP 597635-001 Laptop Keyboard

The jasmonic acid response, is stimulated in leaves damaged by insects, and involves the production of methyl jasmonate. HP Pavilion dv6-2124eo laptop keyboard,HP Pavilion dv5-1044ca laptop keyboard, HP Pavilion dv5-1050ed laptop keyboard

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