Inflammation or inflammation is the body's own reaction to harmful stimuli , which is classically expressed by the signs of inflammation redness, swelling, overheating, pain and functional limitation. Messenger substances of the immune system cause the blood vessels to expand so that the area of inflammation is supplied with more blood; In addition, the vessels become more permeable for blood plasma and immune cells to escape into the tissue . According to another understanding of the term, all immune reactions occurring in certain places are called inflammation. The technical terms for inflammation are formed by adding the ending -itis to the Greek name of the anatomical structure concerned.
Inflammations can ensure the integrity of the organism, for example by removing pathogens or foreign substances from the tissue. Hemostasis and coagulation , inflammation, clearing away cell debris and wound healing are closely interlinked processes that sometimes take place side by side. Inflammation that does more harm than good to the person affected is of great medical importance and a common target of anti-inflammatory treatments .
A foreign substance, antigen or tissue damage triggers the stimulus for a defense reaction of the immune system. The inflammatory reaction takes place in the affected organ , in the surrounding connective tissue , in the blood vessels involved and in the adjacent lymphatic system . This leads to the typical signs of inflammation: reddening (Latin rubor ), overheating (Latin calor ), swelling (Latin tumor ), pain (Latin dolor ) and limited function (Latin functio laesa ). These five characters, of which the first four have already been described by Celsus and the fifth by Galen , are not always directly recognizable or even only partially detectable. An inflammation of the gastric mucosa, for example, can occur e.g. B. cause mainly pain after eating and is then only symptomatic for a limited time . It can be accompanied by nausea.
The reddening and swelling is caused by the increase in the permeability of the blood vessels in the course of diapedesis of the immune cells , erythrocytes and plasma proteins through the release of the messenger substances interleukin-1 and prostaglandin I2 . The immigrated cells and plasma proteins are called the infiltrate. The pain occurs through the release of pain messenger substances ( prostaglandin E2 , prostaglandin I2, bradykinin and other kinins ) and cytokines ( tumor necrosis factor ) by the immune cells and serves to immobilize the body part concerned and to conserve energy reserves through reduced activity. The increase in temperature is mediated by cytokines such as interleukin-6 via the production of prostaglandin E2 and is caused by increased metabolic activity .
Often the response consists of the rejection of part of the diseased tissue through necrosis or apoptosis and subsequent formation of new cells to repair the tissue damage. In skin cells, the rejection of cells serves, among other things, to protect the underlying tissue. Inflammation can occur locally in a (small) area or affect the whole body . Examples of localized inflammation are e.g. B. enteritis (inflammation of the intestines), colitis (inflammation of the colon ), gastritis (inflammation of the stomach), arthritis (inflammation of the joints), myocarditis (inflammation of the heart muscles), dermatitis (inflammation of the skin) and otitis (inflammation of the ear). A linguistic exception is pneumonia (pneumonia), in which the ending "-itis" is missing (although the form pneumonitis is rarely used).
In classical medicine, inflammation is often combated by turning off the triggering stimulus. On the other hand, if the defense reaction is suppressed as part of symptomatic therapy, healing can be delayed.
Any stimulus exceeding the physiological level can cause inflammation. This applies in particular to physical stimuli such as mechanical stimuli (e.g. pressure, friction, injury or foreign bodies , e.g. metabolic products such as uric acid crystals ), thermal stimuli (e.g. heat , cold), radiation (UV, infrared, ionizing radiation ), chemical stimuli (irritating and harmful substances such as acids , bases , toxins , derailed enzymes , such as in acute pancreatitis ), allergens and autoallergens (e.g. in rheumatic or autoimmune diseases ) or Pathogens ( bacteria , viruses , fungi , parasites ).
Course of local inflammatory reactions
- Local reduced blood flow:
- This phase, which lasts only minutes, is also called "initial ischemia ". What is meant is a short-term local reduction in blood flow due to the reaction of the vascular connective tissue to the adrenaline release (arterial spasm ). Dilated venules are connected to the narrowed arterioles.
- This is followed by hyperemia , especially local, which is triggered on the one hand by the arteriolar spasm triggered by the autonomic nervous system and on the other by a narrowing of the venules . The latter is supported by various mediators, e.g. B. prostaglandins , kinins triggered. This drainage disorder in turn leads to platelet aggregation , the sludge phenomenon (viscous blood), exudation and other consequences caused by blood stasis .
- The permeability of the vascular walls is increased for a few minutes by vascular mediators , here histamine , prostaglandins , kinins and serotonin , so that blood congestion occurs.
- Due to the increased permeability, plasma proteins (blood plasma exudation) can now flow into the affected area through gaps in the vessel walls. For the inflammatory response are important here neutrophil mainly basophilic and eosinophilic granulocytes , macrophages and lymphocytes . The foreign bodies are phagocytosed . In addition, more mast cells are washed ashore in the inflamed tissue.
Damage from inflammation
The immune response to noxious agents is not completely specific for them; healthy tissue is always damaged. This is of particular importance in the case of chronic inflammations, in which the elimination of the noxious agent does not succeed and the damage to healthy tissue is therefore very important. Examples of this are pulmonary fibrosis due to asbestos and atherosclerosis due to oxidized lipoproteins , both inflammations that are sustained by macrophages (giant scavenger cells ) that perish when trying to digest the substance to be removed. The inflammatory milieu represents a growth stimulus for smooth muscles , which in atherosclerosis, but also in COPD, intensifies and manifests the loss of function.
Chronic inflammation can trigger neoplasia ( carcinoma or lymphoma ) in many organs and lymphatic tissue and promote their growth and vascular supply. Causes are the chronic stimulus to proliferation , the growth-promoting effect of cytokines and genomic damage by reactive oxygen species that are produced by immune cells (actually to damage the noxious substance).
Inflammations are also problematic when they are directed against the body's own structures or harmless environmental stimuli, such as with autoimmune diseases or allergies . Irrespective of the trigger, inflammations are life-threatening for those affected if they no longer run locally, as in sepsis or septic shock or in the case of very high fever .
General non-specific signs of inflammation
In addition to the five direct signs of inflammation at the site of inflammation, inflammation can be recognized from a certain degree of severity by general reactions of the entire organism. These general reactions include:
- Fever : Accelerated metabolism with faster formation u. a. of antibodies
- general feeling of illness
- Increase or decrease in white blood cells (white blood cells)
- CRP increase (immunologically active acute phase protein )
- accelerated blood cell sedimentation (BKS or ESR for sedimentation speed )
- Procalcitonin -increase ( hormone precursor)
Inflammation is associated with characteristic changes at the molecular level. Initially, the triggering stimuli lead to changes in activity in certain cellular signaling pathways, which in turn lead to specific changes in the gene expression pattern. One of the most important intracellular regulators of inflammatory reactions is, for example, the transcription factor NF-κB , which is activated by bacterial and viral antigens, cytokines and chemical-physical noxae and can change gene expression in affected cells quickly and comprehensively. The upregulated genes include, in particular, cytokines and cell adhesion molecules , which spread the inflammation to other cells and intensify it, often in the form of positive feedback. An example of a molecularly well-characterized inflammatory reaction is the so-called acute phase reaction .
Inflammations can be classified according to the temporal course of the disease :
- peracute, hyperacute = very severe inflammation that sets in suddenly and ends fatally after a few days
- acute = inflammation that sets in suddenly
- subacute = between acute and chronic - no further definition
- primary-chronic = slow, insidious inflammation
- recurrent = recurrent inflammation
- progressive = progressive inflammation (without improvement)
- secondary-chronic = from non-healing acute or recurrent inflammation
after expansion :
- systemic / generalized / metastatic inflammation (whole body - mostly with fever)
- local inflammation (limited to only one spot)
after the liquid :
- serous inflammation (large amounts of protein containing fluid)
- fibrinous inflammation (large amounts of fluid containing fibrin )
- purulent inflammation
- C. Janeway et al .: Immunobiology . 5th edition (2002), ISBN 3-8274-1079-7 . Available online on the NCBI bookshelf pages , (online) .
- H. Lang and H. Greiling: Pathobiochemistry of Inflammation , Springer Verlag (1984), ISBN 3-540-13533-2
- inflammation. In: Pathologie-Online , accessed December 5, 2012.