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Inflammation

Inflammation (from Latin: inflammatio) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants.[1][2] The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin calor, dolor, rubor, tumor, and functio laesa).

Inflammation

Immunology, rheumatology

Heat, pain, redness, swelling

Asthma, pneumonia, autoimmune diseases

Acute: few days
Chronic: up to many months, or years

Infection, physical injury, autoimmune disorder

Inflammation is a generic response, and therefore is considered a mechanism of innate immunity, whereas adaptive immunity is specific to each pathogen.[3]


Inflammation is a protective response involving immune cells, blood vessels, and molecular mediators. The function of inflammation is to eliminate the initial cause of cell injury, clear out damaged cells and tissues, and initiate tissue repair. Too little inflammation could lead to progressive tissue destruction by the harmful stimulus (e.g. bacteria) and compromise the survival of the organism. However inflammation can also have negative effects.[4] Too much inflammation, in the form of chronic inflammation, is associated with various diseases, such as hay fever, periodontal disease, atherosclerosis, and osteoarthritis.


Inflammation can be classified as 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 (in particular granulocytes) from the blood into the injured tissues. A series of biochemical events propagates and matures the inflammatory response, involving the local vascular system, the immune system, and various cells in the injured tissue. Prolonged inflammation, known as chronic inflammation, leads to a progressive shift in the type of cells present at the site of inflammation, such as mononuclear cells, and involves simultaneous destruction and healing of the tissue.


Inflammation has also been classified as Type 1 and Type 2 based on the type of cytokines and helper T cells (Th1 and Th2) involved.[5]


The term inflammation is not a synonym for infection. Infection describes the interaction between the action of microbial invasion and the reaction of the body's inflammatory response—the two components are considered together in discussion of infection, and the word is used to imply a microbial invasive cause for the observed inflammatory reaction. Inflammation, on the other hand, describes just the body's immunovascular response, regardless of cause. But, because of the two are often correlated, words ending in the suffix -itis (which means inflammation) are sometimes informally described as referring to infection: for example, the word urethritis strictly means only "urethral inflammation", but clinical health care providers usually discuss urethritis as a urethral infection because urethral microbial invasion is the most common cause of urethritis.


However, the inflammation–infection distinction is crucial in situations in pathology and medical diagnosis that involve inflammation that is not driven by microbial invasion, such as cases of atherosclerosis, trauma, ischemia, and autoimmune diseases (including type III hypersensitivity).

(pain)

Dolor

Calor (heat)

(redness)

Rubor

Tumor ()

swelling

(loss of function)[17]

Functio laesa

The , when activated, creates a cascade of chemical reactions that promotes opsonization, chemotaxis, and agglutination, and produces the MAC.

complement system

The generates proteins capable of sustaining vasodilation and other physical inflammatory effects.

kinin system

The or clotting cascade, which forms a protective protein mesh over sites of injury.

coagulation system

The , which acts in opposition to the coagulation system, to counterbalance clotting and generate several other inflammatory mediators.

fibrinolysis system

Granulomatous inflammation: Characterised by the formation of , they are the result of a limited but diverse number of diseases, which include among others tuberculosis, leprosy, sarcoidosis, and syphilis.

granulomas

Fibrinous inflammation: Inflammation resulting in a large increase in vascular permeability allows to pass through the blood vessels. If an appropriate procoagulative stimulus is present, such as cancer cells,[9] 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. The deposit sometimes forms a pseudomembrane sheet. During inflammation of the intestine (pseudomembranous colitis), pseudomembranous tubes can be formed.

fibrin

Purulent inflammation: Inflammation resulting in large amount of , 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.

pus

Serous inflammation: Characterised by the copious effusion of non-viscous serous fluid, commonly produced by cells of serous membranes, but may be derived from blood plasma. Skin blisters exemplify this pattern of inflammation.

mesothelial

Ulcerative inflammation: Inflammation occurring near an epithelium can result in the loss of tissue from the surface, exposing lower layers. The subsequent excavation in the epithelium is known as an ulcer.

necrotic

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.

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 microliter, but extreme cases can see it approach 100 000 cells per microliter.[9] 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.[9]

Leukocytosis

can be induced by certain infections and diseases, including viral infection, Rickettsia infection, some protozoa, tuberculosis, and some cancers.[9]

Leukopenia

Acute appendicitis

Acute appendicitis

Acute dermatitis

Acute dermatitis

Acute infective meningitis

Acute infective meningitis

Acute tonsillitis

Acute tonsillitis

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.

at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

Inflammation