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Such biofilms are present in many successful infections, e.g., the chronic Pseudomonas aeruginosaand Burkholderia cenocepacia infections characteristic of cystic fibrosis.[124] Other bacteria generate surface proteins that bind to antibodies, rendering them ineffective; examples include Streptococcus (protein G), Staphylococcus aureus (protein A), and Peptostreptococcus magnus (protein L).[125] DELL Vostro 1018 Series CPU FAN

The mechanisms used to evade the adaptive immune system are more complicated. The simplest approach is to rapidly change non-essential epitopes (amino acidsand/or sugars) on the surface of the pathogen, while keeping essential epitopes concealed. This is called antigenic variation. DELL Vostro 1088 Series CPU FAN

 An example is HIV, which mutates rapidly, so the proteins on its viral envelope that are essential for entry into its host target cell are constantly changing. These frequent changes in antigens may explain the failures of vaccines directed at this virus.[126] The parasite Trypanosoma brucei uses a similar strategy, constantly switching one type of surface protein for another, DELL Vostro 1310 CPU FAN

 allowing it to stay one step ahead of the antibody response.[127] Masking antigens with host molecules is another common strategy for avoiding detection by the immune system. In HIV, the envelope that covers the virion is formed from the outermost membrane of the host cell; such "self-cloaked" viruses make it difficult for the immune system to identify them as "non-self" structures. DELL Vostro 1400 Series CPU FAN
The innate immune system, also known as non-specific immune system and first line of defense,[1] comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner. DELL Vostro 1510 CPU FAN

This means that the cells of the innate system recognize and respond to pathogens in a generic way, but unlike the adaptive immune system (which is only found in vertebrates), it does not confer long-lasting or protective immunity to the host.[2] Innate immune systems provide immediate defense against infection, and are found in all classes of plant and animal life. DELL Vostro 2510 CPU FAN
The innate immune system is an evolutionarily older defense strategy, and is the dominant immune system found in plants,fungi, insects, and in primitive multicellular organisms.[3]The major functions of the vertebrate innate immune system include:Recruiting immune cells to sites of infection, through the production of chemical factors, including specialized chemical mediators, called cytokines. DELL Vostro 3300 CPU FAN
Activation of the complement cascade to identify bacteria, activate cells and to promote clearance of dead cells orantibody complexes.

The identification and removal of foreign substances present in organs, tissues, the blood and lymph, by specialised white blood cells. DELL Vostro 3350 CPU FAN
Activation of the adaptive immune system through a process known as antigen presentation.

Acting as a physical and chemical barrier to infectious agents.

The epithelial surfaces form a physical barrier that is very impermeable to most infectious agents, acting as the first line of defense against invading organisms.[4] DELL Vostro 3400 CPU FAN

 Desquamation of skin epithelium also helps remove bacteria and other infectious agents that have adhered to the epithelial surfaces.[4] In the gastrointestinal and respiratory tract, movement due to peristalsis or cilia, respectively, helps remove infectious agents.[4]Also, mucus traps infectious agents.[4] DELL Vostro 3450 CPU FAN

 The gut flora can prevent the colonization of pathogenic bacteria by secreting toxic substances or by competing with pathogenic bacteria for nutrients or attachment to cell surfaces.[4] The flushing action of tears and saliva helps prevent infection of the eyes and mouth.

Inflammation is one of the first responses of the immune system to infection or irritation. DELL Vostro 3500 CPU FAN
Inflammation is stimulated by chemical factors released by injured cells and serves to establish a physical barrier against the spread of infection, and to promote healing of any damaged tissue following the clearance of pathogens.[5]

The process of acute inflammation is initiated by cells already present in all tissues, DELL Vostro 3700 CPU FAN

 mainly resident macrophages, dendritic cells, histiocytes, Kupffer cells and mastocytes. These cells present receptors, contained on the surface or within the cell, named pattern recognition receptors (PRRs), which recognise molecules that are broadly shared by pathogens but distinguishable from host molecules, DELL Vostro 3700 Series CPU FAN

 collectively referred to as pathogen-associated molecular patterns(PAMPs). At the onset of an infection, burn, or other injuries, these cells undergo activation (one of their PRR recognize a PAMP) and release inflammatory mediators responsible for the clinical signs of inflammation. DELL Vostro 3750 CPU FAN
Chemical factors produced during inflammation (histamine, bradykinin, serotonin, leukotrienes, and prostaglandins) sensitize pain receptors, cause vasodilationof the blood vessels at the scene, and attract phagocytes, especially neutrophils.[5] Neutrophils then trigger other parts of the immune system by releasing factors that summon other leukocytes and lymphocytes. DELL Vostro A840 CPU FAN
Cytokines produced by macrophages and other cells of the innate immune system mediate the inflammatory response. These cytokines include TNF, HMGB1, and IL-1.[6]

The inflammatory response is characterized by the following symptoms: rednessheatswellingpain, and possible dysfunction of the organs or tissues involved. DELL Vostro A860 CPU FAN
The complement system is a biochemical cascade of the immune system that helps, or “complements”, the ability of antibodies to clear pathogens or mark them for destruction by other cells. The cascade is composed of many plasma proteins, synthesised in the liver, primarily by hepatocytes. DELL XPS L501X CPU FAN
The proteins work together to:

§  trigger the recruitment of inflammatory cells.

"tag" pathogens for destruction by other cells by opsonizing, or coating, the surface of the pathogen. DELL XPS L502X CPU FAN
forming holes in the plasma membrane of the pathogen, resulting in cytolysis of the pathogen cell, causing the death of the pathogen.rid the body of neutralised antigen-antibody complexes.

Elements of the complement cascade can be found in many nonmammalian species including plants, birds, fish and some species of invertebrates. DELL XPS M1210 CPU FAN
All white blood cells (WBC) are known as leukocytes. Leukocytes are different from other cells of the body in that they are not tightly associated with a particular organ or tissue; thus, they function similar to independent, single-celled organisms. Leukocytes are able to move freely and interact with and capture cellular debris, foreign particles, or invading microorganisms. DELL XPS M1330 CPU FAN

 Unlike many other cells in the body, most innate immune leukocytes cannot divide or reproduce on their own, but are the products of multipotent hematopoietic stem cells present in the bone marrow.[2]

The innate leukocytes include: Natural killer cells, mast cells, eosinophils, basophils; and the phagocytic cells includingmacrophages, neutrophils and dendritic cells, DELL XPS M140 CPU FAN

and function within the immune system by identifying and eliminating pathogens that might cause infection.

Mast cells are a type of innate immune cell that reside in connective tissue and in the mucous membranes. DELL XPS M1530 CPU FAN

They are intimately associated with defense against pathogens and wound healing, but are also often associated with allergy andanaphylaxis.[5] When activated, mast cells rapidly release characteristic granules, rich in histamine and heparin, along with various hormonal mediators, and chemokines, or chemotactic cytokines into the environment. DELL XPS M170 CPU FAN

Histamine dilates blood vessels, causing the characteristic signs of inflammation, and recruits neutrophils and macrophages.

The word 'phagocyte' literally means 'eating cell'. These are immune cells that engulf, i.e. phagocytose, pathogens or particles. DELL XPS M1710 CPU FAN

To engulf a particle or pathogen, a phagocyte extends portions of its plasma membrane, wrapping the membrane around the particle until it is enveloped (i.e. the particle is now inside the cell). Once inside the cell, the invading pathogen is contained inside an endosome which merges with a lysosome.[3] Compaq Presario CQ42-228LA Laptop Keyboard

The lysosome contains enzymes and acids that kill and digest the particle or organism. Phagocytes generally patrol the body searching for pathogens, but are also able to react to a group of highly specialized molecular signals produced by other cells, called cytokines. The phagocytic cells of the immune system include macrophages, neutrophils, and dendritic cells. HP Pavilion dm1-1010st Laptop Keyboard

Phagocytosis of the hosts’ own cells is common as part of regular tissue development and maintenance. When host cells die, either internally induced by processes involving programmed cell death (also called apoptosis), or caused by cell injury due to a bacterial or viral infection, phagocytic cells are responsible for their removal from the affected site.[2] DELL 454RX Laptop Keyboard

By helping to remove dead cells preceding growth and development of new healthy cells, phagocytosis is an important part of the healing process following tissue injury.

Macrophages, from the Greek, meaning "large eaters," are large phagocytic leukocytes, SAMSUNG R522 Laptop Keyboard

which are able to move outside of the vascular system by moving across the walls of capillary vessels and entering the areas between cells in pursuit of invading pathogens. In tissues, organ-specific macrophages are differentiated from phagocytic cells present in the blood called monocytes.  Compaq Presario CQ57 Series Laptop Keyboard

Macrophages are the most efficient phagocytes, and can phagocytose substantial numbers of bacteria or other cells or microbes.[3] The binding of bacterial molecules to receptors on the surface of a macrophage triggers it to engulf and destroy the bacteria through the generation of a “respiratory burst”, causing the release of reactive oxygen species.TOSHIBA Satellite L755D-SP5165RM Laptop Keyboard

Pathogens also stimulate the macrophage to produce chemokines, which summons other cells to the site of infection.

Neutrophils, along with two other cell types; eosinophils and basophils (see below), are known as granulocytes due to the presence of granules in their cytoplasm, or as polymorphonuclear cells (PMNs) due to their distinctive lobed nuclei.SAMSUNG NP-Q320-FS01UK Laptop Keyboard

Neutrophil granules contain a variety of toxic substances that kill or inhibit growth of bacteria and fungi. Similar to macrophages, neutrophils attack pathogens by activating a respiratory burst. The main products of the neutrophil respiratory burst are strong oxidizing agents including hydrogen peroxide, free oxygen radicals and hypochlorite.  HP G42-364LA Laptop Keyboard

Neutrophils are the most abundant type of phagocyte, normally representing 50 to 60% of the total circulating leukocytes, and are usually the first cells to arrive at the site of an infection.[5] The bone marrow of a normal healthy adult produces more than 100 billion neutrophils per day, and more than 10 times that many per day during acute inflammation.  HP AESP7U00110 Laptop Keyboard

Dendritic cells (DC) are phagocytic cells present in tissues that are in contact with the external environment, mainly the skin (where they are often calledLangerhans cells), and the inner mucosal lining of the nose, lungs, stomach and intestines.[2] They are named for their resemblance to neuronal dendrites, but dendritic cells are not connected to the nervous system. HP G61-425ES Laptop Keyboard

Dendritic cells are very important in the process of antigen presentation, and serve as a link between the innate and adaptive immune systems.

Basophils and eosinophils are cells related to the neutrophil (see above). When activated by a pathogen encounter, basophils releasinghistamine are important in defense against parasites, and play a role in allergic reactions (such as asthma).[3] HP 640436-001 Laptop Keyboard

Upon activation, eosinophils secrete a range of highly toxic proteins and free radicals that are highly effective in killing bacteria and parasites, but are also responsible for tissue damage occurring during allergic reactions. Activation and toxin release by eosinophils is therefore tightly regulated to prevent any inappropriate tissue destruction. Lenovo 3000 N200 Laptop Keyboard

Natural killer cells, or NK cells, are a component of the innate immune system which does not directly attack invading microbes. Rather, NK cells destroy compromised host cells, such as tumor cells or virus-infected cells, recognizing such cells by a condition known as "missing self."  DELL XPS 15 L502X Laptop Keyboard

This term describes cells with low levels of a cell-surface marker called MHC I (major histocompatibility complex) - a situation that can arise in viral infections of host cells.[7] They were named "natural killer" because of the initial notion that they do not require activation in order to kill cells that are "missing self." IBM Lenovo ThinkPad R51 1833 Laptop Keyboard

For many years it was unclear how NK cell recognize tumor cells and infected cells. It is now known that the MHC makeup on the surface of those cells is altered and the NK cells become activated through recognition of "missing self". Normal body cells are not recognized and attacked by NK cells because they express intact self MHC antigens. HP G62-a20EJ Laptop Keyboard

Those MHC antigens are recognized by killer cell immunoglobulin receptors (KIR) which essentially put the breaks on NK cells. The NK-92 cell line does not express KIR and is developed for tumor therapy.

Like other 'unconventional' T cell subsets bearing invariant T cell receptors (TCRs),  ACER Aspire 5742 Laptop Keyboard

such as CD1d-restricted Natural Killer T cells, γδ T cells exhibit characteristics that place them at the border between innate and adaptive immunity. On one hand, γδ T cells may be considered a component of adaptive immunityin that they rearrange TCR genes to produce junctional diversity and develop a memory phenotype. HP Pavilion DV7-3186cl laptop keyboard

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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