- The act of inflaming or the state of being inflamed.
- A localized protective reaction of tissue to irritation, injury, or infection, characterized by pain, redness, swelling, and sometimes loss of function.
inflammation
Dictionary:
in·flam·ma·tion (ĭn'flə-mā'shən)  |
n.
| 5min Related Video: inflammation |
| Sci-Tech Encyclopedia: Inflammation |
The local response to injury, involving small blood vessels, the cells circulating within these vessels, and nearby connective tissue.
The early phases of the inflammatory response are stereotyped: A similar sequence of events occurs in a variety of tissue sites in response to a diversity of injuries. The response characteristically begins with hyperemia, edema, and adherence of the circulating white blood cells to endothelial cells. The white cells then migrate between the endothelial cells of the blood vessel into the tissue. The subsequent development of the inflammatory process is determined by factors such as type and location of injury, immune state of the host, and the use of therapeutic agents. See also Circulation; Edema.
A local inflammatory response is usually accompanied by systemic changes: fever, malaise, an increase in circulating leukocytes (leukocytosis), and increases in specific circulating proteins called acute-phase reactants. Such signals and symptoms are often helpful to the physician, first as clues to the presence of inflammation and later as an indication of its course.
The process of inflammation, both vascular and cellular, is orchestrated by an array of molecules produced locally. These mediators include histamine, leukotrienes, prostaglandins, complement components, kinins, antibodies, and interleukins. Many anti-inflammatory drugs function by preventing the formation of those mediators or by blocking their actions on the target cells whose behavior is modified by the mediators.
Inflammation is basically a protective mechanism. The leakage of water and protein into the injured area brings humoral factors, including antibodies, into the locale and may serve to dilute soluble toxic substances and wash them away. The adherence and migration of leukocytes brings them to the local site to deal with infectious agents. There are also instances in which no causative toxic substance or infectious agent can be found to account for the inflammation. This is the case in rheumatoid arthritis and rheumatic fever. Such diseases may be examples in which an uncontrolled or misdirected inflammatory response with an autoimmune component is turned against the host. See also Arthritis; Autoimmunity; Infection; Rheumatic fever.
| World of the Body: inflammation |
The word incorporates the Greek for flame, and indeed an inflamed body part may feel ‘on fire’. In its traditional clinical description, inflammation has four characteristics: calor (heat), rubor (redness), tumor (swelling and dolor (pain). They are the manifestations of the body's defence against injury or against invasion by foreign material or microorganisms, including the means of removal or destruction of the offending agent, restriction of the spread of infection, and preparations for the healing process. But the immune system that implements vital self-preservation may also sometimes cause inflammation by misdirected attack on some part of the body itself.
Inflammation can occur anywhere, acutely in the skin around a wound or a sting, or in less visible sites such as the lining of the middle ear, or of the bladder, or of the gall bladder. Chronically it can be related to persistent infection, ulceration, mechanical or chemical irritation, or autoimmune disease. Wherever inflammation occurs there are certain local mechanisms in common, despite differences in the precipitating factors and also in the relative prominence of the four cardinal features. Even with relatively minor and apparently localized problems, there are whole-body responses. Wherever inflammation is located, the condition is given a name ending in-itis, prefixed by the traditional name of the body part, such as arthritis for the joints, gastritis for the stomach, pericarditis for the membranes around the heart, ileitis for the small intestine, osteitis for bone, encephalitis for the brain.
Tissue damage results in the release by cells of various chemical agents, including prostaglandins. Vasodilator substances relax the blood vessels in their vicinity and the resulting increase in blood flow accounts for the redness and heat; swelling follows from increased permeability of blood vessels. This all enhances the supply of factors normally present in the blood that are important for the inflammatory response, including white blood cells and certain proteins in the plasma. Locally released substances (cytokines), as well as bacterial toxins if there is infection, attract cells of the immune system — macrophages and lymphocytes.
The nerves that carry the signals, set up by chemical and mechanical stimulation of sensory receptors, that we perceive as pain, themselves in turn promote an increase in local blood flow through the axon reflex mechanism. The nerve fibres (axons) give off branches back to their site of origin, and these release ‘substance P’, a peptide that relaxes the vessel walls. This, together with prostaglandins and other substances released from damaged tissues and also from the macrophages that congregate at the site, increases the sensitivity of sensory nerve endings, enhancing pain.
The events are not confined to the focus of trouble. Cytokines circulating in the blood provoke diverse whole-body responses. A major site of action is the hypothalamus, where they can affect its regulation of pituitary secretions, of sympathetic nervous system activity, and of body temperature. Whilst the resulting responses mainly promote the many aspects of defence, some also modify reactions that might otherwise be excessive: endorphin release modifies pain, and the increase in secretion of corticosteroids has anti-inflammatory effects, including toning down the activity of macrophages and interfering with prostaglandin synthesis.
The manifestations of inflammation vary greatly with the nature and severity of the insult and whether the process is rapidly or slowly developing. It can be simply serous, with fluid exudation, such as in a blister or a swollen joint, or in the rhinitis (of the nose) at the start of a common cold. With some types of infection it can be suppurative, where tissue and immune cell debris form a collection of pus; and chronic inflammation can be granulomatous, with nodules composed of packed inflammatory cells.
The phenomena of inflammation reflect an appropriate response to infection, or to mechanical damage either by acute injury or prolonged pressure or friction. When they occur inappropriately as a reaction against the body's own tissues the manifestations are similar. Thus conditions that might be called ‘inflammatory’ may refer to chronic infections, or to degenerative processes (as in osteoarthritis), or they may result from congenital abnormalities (as in cystic fibrosis) or autoimmune disease (such as rheumatoid arthritis or regional ileitis (Crohn's disease) ).
It would be inappropriate to attempt by treatment to diminish the body's responses, in terms of both local and widespread effects, if and when they were entirely appropriate and necessary to contain or cure the condition. Alleviation of the pain of inflammation by analgesic drugs is clearly beneficial to the sufferer; otherwise the first concern of treatment is if possible to remove the cause (such as treating infection by antibiotics, or removing foreign material). Other treatments in recent decades have been directed against inflammation itself, in conditions related to injury, ‘wear-and-tear’, and auto-immunity. Imitation and enhancement of the body's own anti-inflammatory corticosteroids became possible with synthetic steroid preparations, but there are undesirable side-effects. Along with the understanding of the role of prostaglandins in the mediation of inflammation and fever, a whole family of ‘non-steroidal antiflammatory drugs’ (NSAIDS) were developed, and they are widely used for a variety of muscle and joint problems, from accidental sprains to widespread arthritis. These drugs inhibit enzymes necessary for formation of prostaglandins, thus diminishing their local and general effects. (aspirin was well known to be useful in this context long before it was known to act by this mechanism.) No evidence has emerged for any positive or negative effect on the progress of the underlying conditions themselves (as opposed to relief of the symptoms), supporting the notion that the body's inflammatory responses are not always useful. Symptoms may indeed be relieved, but there are side-effects of NSAIDS, particularly gastrointestinal complications, related to the inhibition of prostaglandin synthesis where and when it is normally needed.
— Sheila Jennett
See also autoimmune diseases; fever; immune system; infection; infectious diseases; injury; pain; prostaglandins.
| Thesaurus: inflammation |
noun
- An instance of being irritated, as in a part of the body: irritation, soreness. See help/harm/harmless.
| Dental Dictionary: inflammation |
(in'fləmā'shən)
n
n
The cellular and vascular response or reaction to injury. Inflammation is characterized by pain, redness, swelling, heat, and disturbance of function. It may be acute or chronic. The term is not synonymous with infection, which implies an inflammatory reaction initiated by invasion of living organisms.
| Britannica Concise Encyclopedia: inflammation |
For more information on inflammation, visit Britannica.com.
| Sports Science and Medicine: inflammation |
inflammatory response
non-specific defensive response of tissues to a physical or chemical injury, or bacterial infection. The response includes dilation (widening) of blood vessels and an increase in vessel permeability. It is indicated by redness, heat, swelling, pain, and dysfunction. Inflammation destroys, dilutes, or isolates the injurious agent and the injured tissue. Non-steroidal anti-inflammatories are often used to alleviate the symptoms and localize the inflammatory response. Some physical therapies (e.g. ultrasound) actually accelerate the inflammatory response, stimulating the activity of mast cells (large cells in connective tissue, which produce inflammatory chemicals) and accelerating the normal repair process. Chronic inflammatory conditions caused by overuse injuries can be self-perpetuating and require strong anti-inflammatories (e.g. steroid injections) to resolve them.
| Columbia Encyclopedia: inflammation |
inflammation, reaction of the body to injury or to infectious, allergic, or chemical irritation. The symptoms are redness, swelling, heat, and pain resulting from dilation of the blood vessels in the affected part with loss of plasma and leucocytes (white blood cells) into the tissues. White blood cells communicate with each other via cytokines, which are polypeptides released by cells of the immune system that regulate other cells. They are a broad class of soluble compounds that signal one cell type to another, particularly in response to foreign substances. Granulomas are most common in infectious diseases such as tuberculosis, leishmaniasis, and schistosomiasis, in which the body's defenses, unable to destroy the offending organisms, try to enclose them in a mass of inflammatory cells. Certain types of inflammation result in pus formation, as in an abscess. The leukocytes destroy harmful microorganisms and dead cells, preventing the spread of the irritation and permitting the injured tissue to repair itself.
| Health Dictionary: inflammation |
The response of tissue to injury or infection. Pain, heat, redness, and swelling are the four basic symptoms of inflammation.
| Veterinary Dictionary: inflammation |
A localized protective response elicited by injury or destruction of tissues, which serves to destroy, dilute, or wall off both the injurious agent and the injured tissue.
The inflammatory response can be provoked by physical, chemical and biological agents, including mechanical trauma, exposure to excessive amounts of sunlight, x-rays and radioactive materials, corrosive chemicals, extremes of heat and cold, and infectious agents such as bacteria, viruses and other pathogenic microorganisms. Although these infectious agents can produce inflammation, infection and inflammation are not synonymous.
The classic signs of inflammation are heat, redness, swelling, pain and loss of function. These are manifestations of the physiological changes that occur during the inflammatory process. The three major components of this process are: (1) changes in the caliber of blood vessels and the rate of blood flow through them (hemodynamic changes); (2) increased capillary permeability; and (3) leukocytic exudation.
- acute i. — inflammation, usually of sudden onset, marked by the classic signs of heat, redness, swelling, pain and loss of function, and in which vascular and exudative processes predominate.
- adhesive i. — promotes adhesion of adjacent surfaces.
- atrophic i. — one that causes atrophy and deformity.
- catarrhal i. — a form affecting mainly a mucous surface, marked by a copious discharge of mucus and epithelial debris.
- chronic i. — prolonged and persistent inflammation marked chiefly by new connective tissue formation; it may be a continuation of an acute form or a prolonged low-grade form.
- chronic i. bowel disease of sheep — a syndrome of unknown etiology, manifest with wasting, ill thrift and mortality or culling for poor production. Reported in England and Canada, it affects both housed and pastured sheep, predominantly in their first year of life, but cases up to three years-of-age have been seen. Affected sheep are dull and anorectic with pale mucous membranes and have fecal staining of the perineum. The rumen fill is reduced and the feces are soft and malodorous. Blood examination shows hypoalbuminemia, an elevated blood urea nitrogen and leukocytosis with neutrophilia. On postmortem there is a lymphocytic enteritis with gross thickening of segments or the entire or distal part of the small intestine. There is no evidence for Johne's disease or parasitic gastroenteritis and the syndrome has similarities to the proliferative enteropathies of swine and horses.
- croupous i. — a homogeneous layer of exudate lying close to but detached from the underlying inflamed tissue, which is comparatively unharmed; may form a fibrinous cast.
- diphtheritic i. — manifested by the development of a fibrinous exudate which is firmly attached to the underlying tissue, such that it cannot be removed except by tearing off a superficial layer.
- exudative i. — one in which the prominent feature is an exudate.
- fibrinous i. — one marked by an exudate of coagulated fibrin.
- fibrous i. — leads to the development of fibrous tissue.
- granulomatous i. — a form, usually chronic, attended by formation of granulomas.
- hyperplastic i. — leads to the development of new connective tissue.
- hypertrophic i. — leading to the enlargement of the affected tissues.
- interstitial i. — inflammation affecting chiefly the stroma of an organ.
- obliterative i. — inflammation within a vessel or viscus leading to occlusion of the lumen.
- parenchymatous i. — inflammation affecting chiefly the essential tissue elements of an organ.
- productive i., proliferative i. — one leading to the production of new connective tissue fibers.
- pseudomembranous i. — an acute inflammatory response to a powerful necrotizing toxin, e.g. Fusobacterium necrophorum toxin, characterized by formation on a mucosal surface of a false membrane composed of precipitated fibrin, necrotic epithelium and inflammatory leukocytes. See also diphtheritic inflammation (above).
- purulent i. — suppurative inflammation.
- serous i. — one producing a serous exudate.
- specific i. — one due to a particular microorganism.
- systemic i. response syndrome (SIRS) — a generalized inflammatory response with vasodilation of capillaries and postcapillary venules, increased permeability of capillaries, and hypovolemia. Depressed cardiac function and decreased organ perfusion follow. The various initiating stimuli include sepsis and septic shock, hyperthermia, pancreatitis, trauma, snake bite and immune-mediated diseases.
- toxic i. — one due to a poison, e.g. a bacterial product.
- traumatic i. — one that follows a wound or injury.
- ulcerative i. — that in which necrosis on or near the surface leads to loss of tissue and creation of a local defect or ulcer.
| Wikipedia: Inflammation |
"Inflammatory" redirects here. For the behavior description, see Troll (Internet).
Inflammation (Latin, inflammatio, a setting on fire) is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants.[1] Inflammation is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue. Inflammation is not a synonym for infection. Even in cases where inflammation is caused by infection, the two are not synonymous: infection is caused by an exogenous pathogen, while inflammation is one of the responses of the organism to the pathogen.
In the absence of inflammation, wounds and infections would never heal and progressive destruction of the tissue would compromise the survival of the organism. However, chronic inflammation can also lead to a host of diseases, such as hay fever, atherosclerosis, and rheumatoid arthritis. It is for that reason that inflammation is normally closely regulated by the body.
Inflammation can be classified as either acute or chronic. Acute inflammation is the initial response of the body to harmful stimuli and is achieved by the increased movement of plasma and leukocytes from the blood into the injured tissues. A cascade of biochemical events propagates and matures the inflammatory response, involving the local vascular system, the immune system, and various cells within the injured tissue. Prolonged inflammation, known as chronic inflammation, leads to a progressive shift in the type of cells which are present at the site of inflammation and is characterized by simultaneous destruction and healing of the tissue from the inflammatory process.
Contents |
Causes
- Burns
- Chemical irritants
- Frostbite
- Toxins
- Infection by pathogens
- Physical injury, blunt or penetrating
- Immune reactions due to hypersensitivity
- Ionizing radiation
- Foreign bodies, including splinters and dirt
Types
| Acute | Chronic | |
|---|---|---|
| Causative agent | Pathogens, injured tissues | Persistent acute inflammation due to non-degradable pathogens, persistent foreign bodies, or autoimmune reactions |
| Major cells involved | Neutrophils, mononuclear cells (monocytes, macrophages) | Mononuclear cells (monocytes, macrophages, lymphocytes, plasma cells), fibroblasts |
| Primary mediators | Vasoactive amines, eicosanoids | IFN-γ and other cytokines, growth factors, reactive oxygen species, hydrolytic enzymes |
| Onset | Immediate | Delayed |
| Duration | Few days | Up to many months, or years |
| Outcomes | Resolution, abscess formation, chronic inflammation | Tissue destruction, fibrosis |
Clinical signs
| English | Latin | |
|---|---|---|
| Redness | Rubor* | |
| Swelling | Tumor/Turgor* | |
| Heat | Calor* | |
| Pain | Dolor* | |
| Loss of function | Functio laesa** | |
| All the above signs may be observed in specific instances, but no single sign must, as a matter of course, be present.[2]
These are the original, so called, "cardinal signs" of inflammation.[2]* Functio laesa is a bit of an apocryphal notion, as it is not really unique to inflammation and is a characteristic of many disease states.[3]** |
||
Acute inflammation is a short-term process, usually appearing within a few minutes or hours and ceasing upon the removal of the injurious stimulus.[4]. It is characterized by five cardinal signs:[5]
- rubor (redness),
- calor (increased heat),
- tumor (swelling),
- dolor (pain), and
- functio laesa (loss of function).
The first four (classical signs) were described by Celsus (ca 30 BC–38 AD), while loss of function was added later by Galen[6] even though the attribution is disputed and the origination of the fifth sign has also been ascribed to Thomas Sydenham[7] and Virchow.[4][5]
Redness and heat are due to increased blood flow at body core temperature to the inflamed site; swelling is caused by accumulation of fluid; pain is due to release of chemicals that stimulate nerve endings. Loss of function has multiple causes.[5]
These five signs appear when acute inflammation occurs on the body's surface, whereas acute inflammation of internal organs may not result in the full set. Pain only happens where the appropriate sensory nerve endings exist in the inflamed area — e.g., acute inflammation of the lung (pneumonia) does not cause pain unless the inflammation involves the parietal pleura, which does have pain-sensitive nerve endings.[5]
Process of acute inflammation
The process of acute inflammation is initiated by cells already present in all tissues, mainly resident macrophages, dendritic cells, histiocytes, Kuppfer cells and mastocytes. At the onset of an infection, burn, or other injuries, these cells undergo activation and release inflammatory mediators responsible for the clinical signs of inflammation. Vasodilation and its resulting increased blood flow causes the redness (rubor) and increased heat (calor). Increased permeability of the blood vessels results in an exudation (leakage) of plasma proteins and fluid into the tissue (oedema), which manifests itself as swelling (tumor). Some of the released mediators such as bradykinin increase the sensitivity to pain (hyperalgesia, dolor). The mediator molecules also alter the blood vessels to permit the migration of leukocytes, mainly neutrophils, outside of the blood vessels (extravasation) into the tissue. The neutrophils migrate along a chemotactic gradient created by the local cells to reach the site of injury.[4] The loss of function (functio laesa) is probably the result of a neurological reflex in response to pain.
In addition to cell-derived mediators, several acellular biochemical cascade systems consisting of preformed plasma proteins act in parallel to initiate and propagate the inflammatory response. These include the complement system activated by bacteria, and the coagulation and fibrinolysis systems activated by necrosis, e.g. a burn or a trauma.[4]
The acute inflammatory response requires constant stimulation to be sustained. Inflammatory mediators have short half lives and are quickly degraded in the tissue. Hence, inflammation ceases once the stimulus has been removed.[4]
Exudative component
The exudative component involves the movement of plasma fluid, containing important proteins such as fibrin and immunoglobulins (antibodies), into inflamed tissue. This movement is achieved via the chemically induced dilation and increased permeability of blood vessels, which results in a net loss of blood plasma. The increased collection of fluid into the tissue causes it to swell (edema).
Vascular changes
Acute inflammation is characterised by marked vascular changes, including vasodilation, increased permeability, and the slowing of blood flow, which are induced by the actions of various inflammatory mediators. Vasodilation occurs first at the arteriole level, progressing to the capillary level, and brings about a net increase in the amount of blood present, causing the redness and heat of inflammation. Increased permeability of the vessels results in the movement of plasma into the tissues, with resultant stasis due to the increase in the concentration of the cells within blood - a condition characterised by enlarged vessels packed with cells. Stasis allows leukocytes to marginate (move) along the endothelium, a process critical to their recruitment into the tissues. Normal flowing blood prevents this, as the shearing force along the periphery of the vessels moves cells in the blood into the middle of the vessel.
Plasma cascade systems
- The complement system, when activated, results in the increased removal of pathogens via opsonisation and phagocytosis.
- The kinin system generates proteins capable of sustaining vasodilation and other physical inflammatory effects.
- The coagulation system or clotting cascade which forms a protective protein mesh over sites of injury.
- The fibrinolysis system, which acts in opposition to the coagulation system, to counterbalance clotting and generate several other inflammatory mediators.
Plasma derived mediators
* non-exhaustive list
| Name | Produced by | Description |
|---|---|---|
| Bradykinin | Kinin system | A vasoactive protein which is able to induce vasodilation, increase vascular permeability, cause smooth muscle contraction, and induce pain. |
| C3 | Complement system | Cleaves to produce C3a and C3b. C3a stimulates histamine release by mast cells, thereby producing vasodilation. C3b is able to bind to bacterial cell walls and act as an opsonin, which marks the invader as a target for phagocytosis. |
| C5a | Complement system | Stimulates histamine release by mast cells, thereby producing vasodilation. It is also able to act as a chemoattractant to direct cells via chemotaxis to the site of inflammation. |
| Factor XII (Hageman Factor) | Liver | A protein which circulates inactively, until activated by collagen, platelets, or exposed basement membranes via conformational change. When activated, it in turn is able to activate three plasma systems involved in inflammation: the kinin system, fibrinolysis system, and coagulation system. |
| Membrane attack complex | Complement system | A complex of the complement proteins C5b, C6, C7, C8, and multiple units of C9. The combination and activation of this range of complement proteins forms the membrane attack complex, which is able to insert into bacterial cell walls and causes cell lysis with ensuing death. |
| Plasmin | Fibrinolysis system | Able to break down fibrin clots, cleave complement protein C3, and activate Factor XII. |
| Thrombin | Coagulation system | Cleaves the soluble plasma protein fibrinogen to produce insoluble fibrin, which aggregates to form a blood clot. Thrombin can also bind to cells via the PAR1 receptor to trigger several other inflammatory responses, such as production of chemokines and nitric oxide. |
Cellular component
The cellular component involves leukocytes, which normally reside in blood and must move into the inflamed tissue via extravasation to aid in inflammation. Some act as phagocytes, ingesting bacteria, viruses, and cellular debris. Others release enzymatic granules which damage pathogenic invaders. Leukocytes also release inflammatory mediators which develop and maintain the inflammatory response. Generally speaking, acute inflammation is mediated by granulocytes, while chronic inflammation is mediated by mononuclear cells such as monocytes and lymphocytes.
Leukocyte extravasation
Main article: Leukocyte extravasation
Various leukocytes are critically involved in the initiation and maintenance of inflammation. These cells must be able to get to the site of injury from their usual location in the blood, therefore mechanisms exist to recruit and direct leukocytes to the appropriate place. The process of leukocyte movement from the blood to the tissues through the blood vessels is known as extravasation, and can be divided up into a number of broad steps:
- Leukocyte localisation and recruitment to the endothelium local to the site of inflammation – involving margination and adhesion to the endothelial cells: Recruitment of leukocytes is receptor-mediated. The products of inflammation, such as histamine, promote the immediate expression of P-selectin on endothelial cell surfaces. This receptor binds weakly to carbohydrate ligands on leukocyte surfaces and causes them to "roll" along the endothelial surface as bonds are made and broken. Cytokines from injured cells induce the expression of E-selectin on endothelial cells, which functions similarly to P-selectin. Cytokines also induce the expression of integrin ligands on endothelial cells, which further slow leukocytes down. These weakly bound leukocytes are free to detach if not activated by chemokines produced in injured tissue. Activation increases the affinity of bound integrin receptors for ligands on the endothelial cell surface, firmly binding the leukocytes to the endothelium.
- Migration across the endothelium, known as transmigration, via the process of diapedesis: Chemokine gradients stimulate the adhered leukocytes to move between endothelial cells and pass the basement membrane into the tissues.
- Movement of leukocytes within the tissue via chemotaxis: Leukocytes reaching the tissue interstitium bind to extracellular matrix proteins via expressed integrins and CD44 to prevent their loss from the site. Chemoattractants cause the leukocytes to move along a chemotactic gradient towards the source of inflammation.
Cell derived mediators
* non-exhaustive list
| Name | Type | Source | Description |
|---|---|---|---|
| Lysosome granules | Enzymes | Granulocytes | These cells contain a large variety of enzymes which perform a number of functions. Granules can be classified as either specific or azurophilic depending upon the contents, and are able to break down a number of substances, some of which may be plasma-derived proteins which allow these enzymes to act as inflammatory mediators. |
| Histamine | Vasoactive amine | Mast cells, basophils, platelets | Stored in preformed granules, histamine is released in response to a number of stimuli. It causes arteriole dilation and increased venous permeability. |
| IFN-γ | Cytokine | T-cells, NK cells | Antiviral, immunoregulatory, and anti-tumour properties. This interferon was originally called macrophage-activating factor, and is especially important in the maintenance of chronic inflammation. |
| IL-8 | Chemokine | Primarily macrophages | Activation and chemoattraction of neutrophils, with a weak effect on monocytes and eosinophils. |
| Leukotriene B4 | Eicosanoid | Leukocytes | Able to mediate leukocyte adhesion and activation, allowing them to bind to the endothelium and migrate across it. In neutrophils, it is also a potent chemoattractant, and is able to induce the formation of reactive oxygen species and the release of lysosome enzymes by these cells. |
| Nitric oxide | Soluble gas | Macrophages, endothelial cells, some neurons | Potent vasodilator, relaxes smooth muscle, reduces platelet aggregation, aids in leukocyte recruitment, direct antimicrobial activity in high concentrations. |
| Prostaglandins | Eicosanoid | Mast cells | A group of lipids which can cause vasodilation, fever, and pain. |
| TNF-α and IL-1 | Cytokines | Primarily macrophages | Both affect a wide variety of cells to induce many similar inflammatory reactions: fever, production of cytokines, endothelial gene regulation, chemotaxis, leukocyte adherence, activation of fibroblasts. Responsible for the systemic effects of inflammation, such as loss of appetite and increased heart rate. |
Morphologic patterns
Specific patterns of acute and chronic inflammation are seen during particular situations that arise in the body, such as when inflammation occurs on an epithelial surface, or pyogenic bacteria are involved.
- Granulomatous inflammation: Characterised by the formation of granulomas, they are the result of a limited but diverse number of diseases, which include among others tuberculosis, leprosy, and syphilis.
- Fibrinous inflammation: Inflammation resulting in a large increase in vascular permeability allows fibrin to pass through the blood vessels. If an appropriate procoagulative stimulus is present, such as cancer cells,[4] a fibrinous exudate is deposited. This is commonly seen in serous cavities, where the conversion of fibrinous exudate into a scar can occur between serous membranes, limiting their function.
- Purulent inflammation: Inflammation resulting in large amount of pus, which consists of neutrophils, dead cells, and fluid. Infection by pyogenic bacteria such as staphylococci is characteristic of this kind of inflammation. Large, localised collections of pus enclosed by surrounding tissues are called abscesses.
- Serous inflammation: Characterised by the copious effusion of non-viscous serous fluid, commonly produced by mesothelial cells of serous membranes, but may be derived from blood plasma. Skin blisters exemplify this pattern of inflammation.
- Ulcerative inflammation: Inflammation occurring near an epithelium can result in the necrotic loss of tissue from the surface, exposing lower layers. The subsequent excavation in the epithelium is known as an ulcer.
Inflammatory disorders
Abnormalities associated with inflammation comprise a large, officially unrelated group of disorders which underlie a vast variety of human diseases. The immune system is often involved with inflammatory disorders, demonstrated in both allergic reactions and some myopathies, with many immune system disorders resulting in abnormal inflammation. Non-immune diseases with a etiological origins in inflammatory processes are thought to include cancer, atherosclerosis, and ischaemic heart disease.[4]
A large variety of proteins are involved in inflammation, and any one of them is open to a genetic mutation which impairs or otherwise dysregulates the normal function and expression of that protein.
Examples of disorders associated with inflammation include:
Allergies
An allergic reaction, formally known as type 1 hypersensitivity, is the result of an inappropriate immune response triggering inflammation. A common example is hay fever, which is caused by a hypersensitive response by skin mast cells to allergens. Pre-sensitised mast cells respond by degranulating, releasing vasoactive chemicals such as histamine. These chemicals propagate an excessive inflammatory response characterised by blood vessel dilation, production of pro-inflammatory molecules, cytokine release, and recruitment of leukocytes.[4] Severe inflammatory response may mature into a systemic response known as anaphylaxis.
Other hypersensitivity reactions (type 2 and type 3) are mediated by antibody reactions and induce inflammation by attracting leukocytes which damage surrounding tissue.[4]
Myopathies
Inflammatory myopathies are caused by the immune system inappropriately attacking components of muscle, leading to signs of muscle inflammation. They may occur in conjunction with other immune disorders, such as systemic sclerosis, and include dermatomyositis, polymyositis, and inclusion body myositis.[4]
Leukocyte defects
Due to the central role of leukocytes in the development and propagation of inflammation, defects in leukocyte function often result in a decreased capacity for inflammatory defense with subsequent vulnerability to infection.[4] Dysfunctional leukocytes may be unable to correctly bind to blood vessels due to surface receptor mutations, digest bacteria (Chediak-Higashi syndrome), or produce microbicides (chronic granulomatous disease). Additionally, diseases affecting the bone marrow may result in abnormal or few leukocytes.
Pharmacological
Certain drugs or exogenic chemical compounds are known to affect inflammation. Vitamin A deficiency causes an increase in inflammatory responses,[8] and anti-inflammatory drugs work specifically by inhibiting normal inflammatory components.
Cancer
Inflammation orchestrates the microenvironment around tumours, contributing to proliferation, survival and migration. Cancer cells use selectins, chemokines and their receptors for invasion, migration and metastasis.[9] On the other hand, many cells of the immune system contribute to cancer immunology, suppressing cancer.
Termination
The inflammatory response must be actively terminated when no longer needed to prevent unnecessary "bystander" damage to tissues.[4] Failure to do so results in chronic inflammation, cellular destruction, and attempts to heal the inflamed tissue. One intrinsic mechanism employed to terminate inflammation is the short half-life of inflammatory mediators in vivo. They have a limited time frame to affect their target before breaking down into non-functional components, therefore constant inflammatory stimulation is needed to propagate their effects.
Active mechanisms which serve to terminate inflammation include[4]:
- TGF-β from macrophages
- Anti-inflammatory lipoxins
- Inhibition of pro-inflammatory molecules, such as leukotrienes
| “ | Acute inflammation normally resolves by mechanisms that have remained somewhat elusive. Emerging evidence now suggests that an active, coordinated program of resolution initiates in the first few hours after an inflammatory response begins. After entering tissues, granulocytes promote the switch of arachidonic acid–derived prostaglandins and leukotrienes to lipoxins, which initiate the termination sequence. Neutrophil recruitment thus ceases and programmed death by apoptosis is engaged. These events coincide with the biosynthesis, from omega-3 polyunsaturated fatty acids, of resolvins and protectins, which critically shorten the period of neutrophil infiltration by initiating apoptosis. Consequently, apoptotic neutrophils undergo phagocytosis by macrophages, leading to neutrophil clearance and release of anti-inflammatory and reparative cytokines such as transforming growth factor-Β1. The anti-inflammatory program ends with the departure of macrophages through the lymphatics.[10] | ” |
|
—Charles Serhan |
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Systemic effects
An infectious organism can escape the confines of the immediate tissue via the circulatory system or lymphatic system, where it may spread to other parts of the body. If an organism is not contained by the actions of acute inflammation it may gain access to the lymphatic system via nearby lymph vessels. An infection of the lymph vessels is known as lymphangitis, and infection of a lymph node is known as lymphadenitis. A pathogen can gain access to the bloodstream through lymphatic drainage into the circulatory system.
When inflammation overwhelms the host, systemic inflammatory response syndrome is diagnosed. When it is due to infection, the term sepsis is applied, with bacteremia being applied specifically for bacterial sepsis and viremia specifically to viral sepsis. Vasodilation and organ dysfunction are serious problems associated with widespread infection that may lead to septic shock and death.
Acute-phase proteins
Inflammation also induces high systemic levels of acute-phase proteins. In acute inflammation, these proteins prove beneficial, however in chronic inflammation they can contribute to amyloidosis.[4] These proteins include C-reactive protein, serum amyloid A, and serum amyloid P, vasopressin, which cause a range of systemic effects including[4]:
- Fever
- Increased blood pressure
- Decreased sweating
- Malaise
- Loss of appetite
- Somnolence
Leukocyte numbers
Inflammation often affects the numbers of leukocytes present in the body:
- Leukocytosis is often seen during inflammation induced by infection, where it results in a large increase in the amount of leukocytes in the blood, especially immature cells. Leukocyte numbers usually increase to between 15 000 and 20 000 cells per ml, but extreme cases can see it approach 100 000 cells per ml.[4] Bacterial infection usually results in an increase of neutrophils, creating neutrophilia, whereas diseases such as asthma, hay fever, and parasite infestation result in an increase in eosinophils, creating eosinophilia.[4]
- Leukopenia can be induced by certain infections and diseases, including viral infection, Rickettsia infection, some protozoa, tuberculosis, and some cancers.[4]
Systemic inflammation and obesity
With the discovery of interleukins (IL), the concept of systemic inflammation developed. Although the processes involved are identical to tissue inflammation, systemic inflammation is not confined to a particular tissue but involves the endothelium and other organ systems.
High levels of several inflammation-related markers such as IL-6, IL-8, and TNF-α are associated with obesity.[11][12] During clinical studies, inflammatory-related molecule levels were reduced and increased levels of anti-inflammatory molecules were seen within four weeks after patients began a very low calorie diet.[13] The association of systemic inflammation with insulin resistance and atherosclerosis is the subject of intense research.[14]
Outcomes
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The outcome in a particular circumstance will be determined by the tissue in which the injury has occurred and the injurious agent that is causing it. Here are the possible outcomes to inflammation:[4]
- Resolution
The complete restoration of the inflamed tissue back to a normal status. Inflammatory measures such as vasodilation, chemical production, and leukocyte infiltration cease, and damaged parenchymal cells regenerate. In situations where limited or short lived inflammation has occurred this is usually the outcome. - Fibrosis
Large amounts of tissue destruction, or damage in tissues unable to regenerate, can not be regenerated completely by the body. Fibrous scarring occurs in these areas of damage, forming a scar composed primarily of collagen. The scar will not contain any specialized structures, such as parenchymal cells, hence functional impairment may occur. - Abscess Formation
A cavity is formed containing pus, an opaque liquid containing dead white blood cells and bacteria with general debris from destroyed cells. - Chronic inflammation
In acute inflammation, if the injurious agent persists then chronic inflammation will ensue. This process, marked by inflammation lasting many days, months or even years, may lead to the formation of a chronic wound. Chronic inflammation is characterised by the dominating presence of macrophages in the injured tissue. These cells are powerful defensive agents of the body, but the toxins they release (including reactive oxygen species) are injurious to the organism's own tissues as well as invading agents. Consequently, chronic inflammation is almost always accompanied by tissue destruction.
Examples
Inflammation is usually indicated by adding the suffix "-itis", as shown below. However, some conditions such as asthma and pneumonia do not follow this convention. More examples are available at list of types of inflammation.
 Acute appendicitis |
 Acute dermatitis |
 Acute infective meningitis |
 Acute tonsillitis |
See also
 |
Wikimedia Commons has media related to: Inflammation |
References
- ^ Ferrero-Miliani L, Nielsen OH, Andersen PS, Girardin SE (February 2007). "Chronic inflammation: importance of NOD2 and NALP3 in interleukin-1beta generation". Clin. Exp. Immunol. 147 (2): 227–35. doi:. PMID 17223962.
- ^ a b Stedman's Medical Dictionary, Twenty-fifth Edition, Williams & Wilkins, 1990.
- ^ Disturbance of function (functio laesa): the legendary fifth cardinal sign of inflammation, added by Galen to the four cardinal signs of Celsus. Bull N Y Acad Med. 1971 March; 47(3): 303–322
- ^ a b c d e f g h i j k l m n o p q r s Cotran; Kumar, Collins (1998). Robbins Pathologic Basis of Disease. Philadelphia: W.B Saunders Company. ISBN 0-7216-7335-X.
- ^ a b c d Parakrama Chandrasoma, Clive R. Taylor (ca. 2005). "Part A. General Pathology, Section II. The Host Response to Injury, Chapter 3. The Acute Inflammatory Response, sub-section Cardinal Clinical Signs". Concise Pathology (3rd edition (Computer file) ed.). New York, N.Y.: McGraw-Hill. ISBN 0838514995. OCLC 150148447. http://www.accessmedicine.com/content.aspx?aID=183351. Retrieved 2008-11-05.
- ^ Porth, Carol (2007). Essentials of pahtophysiology: concepts of altered health states. Hagerstown, MD: Lippincott Williams & Wilkins. pp. 270. ISBN 0-7817-7087-4.
- ^ Dormandy, Thomas (2006). The worst of evils: man's fight against pain. New Haven, Conn: Yale University Press. pp. 22. ISBN 0-300-11322-6.
- ^ Wiedermann U, et al. (1996). "Vitamin A deficiency increases inflammatory responses.". Scand J Immunol. 44 (6): 578–84. doi:. PMID 8972739. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&list_uids=8972739&cmd=Retrieve.
- ^ Coussens LM, Werb Z (2002). "Inflammation and cancer". Nature 420 (6917): 860–7. doi:. PMID 12490959.
- ^ Serhan CN, Savill J (2005). "Resolution of inflammation: the beginning programs the end". Nat. Immunol. 6 (12): 1191–7. doi:. PMID 16369558. http://www.nature.com/ni/journal/v6/n12/abs/ni1276.html.
- ^ Bastard J et al. (2000). "Elevated levels of interleukin 6 are reduced in serum and subcutaneous adipose tissue of obese women after weight loss". J Clin Endocrinol Metab 85 (9): 3338–42. doi:. PMID 10999830. http://jcem.endojournals.org/cgi/content/full/85/9/3338?ijkey=c94031a625120a7e59ea52e88137260e974cee3a.
- ^ Mohamed-Ali V et al. (2001). "beta-Adrenergic regulation of IL-6 release from adipose tissue: in vivo and in vitro studies". J Clin Endocrinol Metab 86 (12): 5864–9. doi:. PMID 11739453. http://jcem.endojournals.org/cgi/content/full/86/12/5864?ijkey=838bb038c4e311324ab354c88ea16afe51d6e823.
- ^ Clément K et al. (2004). "Weight loss regulates inflammation-related genes in white adipose tissue of obese subjects". Faseb J 18 (14): 1657–69. doi:. PMID 15522911. http://www.fasebj.org/cgi/content/full/18/14/1657.
- ^ M Stitzinger (2007). "Lipids, inflammation and atherosclerosis" (pdf). The digital repository of Leiden University. https://openaccess.leidenuniv.nl/dspace/bitstream/1887/9729/11/01.pdf. Retrieved 2007-11-02.
Further reading
Kyriakis JM, Avruch J. Sounding the alarm: protein kinase cascades activated by stress and inflammation. J Biol Chem. 1996 Oct 4;271(40):24313-6. Review. PMID: 8798679
Salminen A, Kauppinen A, Suuronen T, Kaarniranta K. SIRT1 longevity factor suppresses NF-kappaB -driven immune responses: regulation of aging via NF-kappaB acetylation? Bioessays. 2008 Oct;30(10):939-42.
Rangan G, Wang Y, Harris D. NF-kappaB signalling in chronic kidney disease. Front Biosci. 2009 Jan 1;14:3496-522. Review. PMID: 19273289
External links
- What You Need to Know About Inflammation at Cleveland Clinic
- Anti-Inflammatory Diet - Foods and Inflammation at About.com
- MeSH Inflammation
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| Misspellings: inflammation |
Common misspelling(s) of inflammation
- inflamation
| Translations: Inflammation |
Dansk (Danish)
n. - antændelse, betændelse, inflammation
idioms:
- inflammation of the bladder blærebetændelse
Nederlands (Dutch)
ontsteking, ontbranding
Français (French)
n. - (Méd) inflammation, inflammation (d'un combustible), (fig) excitation
Deutsch (German)
n. - Entzündung, Aufflammen, Aufstacheln
Ελληνική (Greek)
n. - (ιατρ.) φλεγμονή, (μτφ.) έξαψη, παροξυσμός, ερεθισμός
idioms:
- inflammation of the bladder κυστίτιδα
Italiano (Italian)
combustione, infiammazione
Português (Portuguese)
n. - inflamação (f)
Русский (Russian)
воспламенение, воспаление
Español (Spanish)
n. - combustión, inflamación
Svenska (Swedish)
n. - inflammation, upphetsning, antändning
中文（简体）(Chinese (Simplified))
怒火, 燃烧, 发火
idioms:
- inflammation of the bladder 膀胱炎
中文（繁體）(Chinese (Traditional))
n. - 怒火, 燃燒, 發火
idioms:
- inflammation of the bladder 膀胱炎
한국어 (Korean)
n. - 점화, 연소, 염증 , 격노
日本語 (Japanese)
n. - 点火, 燃焼, 燃え上がり, 炎症, 発火
idioms:
- inflammation of the bladder 膀胱炎
العربيه (Arabic)
(الاسم) التهاب, اشتعال
עברית (Hebrew)
n. - דלקת, הדלקה, שלהוב
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