Autoimmunity is a malfunction of the immune system. In autoimmune diseases, the body loses tolerance to the body's own structures. Chronic inflammation occurs as a result.
What is the autoimmunity?
Autoimmunity is the inability of the body to recognize its tissue structures as the body's own. The immune system reacts incorrectly and attacks its own tissue.
The result is chronic inflammation. Different tissues can be affected by the attacks of the immune system. Well-known autoimmune diseases are multiple sclerosis, Hashimoto's thyroiditis or lupus erythematosus.
Function & task
The immune system can be divided into a specific and a non-specific defense. The main cells of the specific defense are the B and T lymphocytes. They mature in the bone marrow and thymus. In the lymph tissues of the spleen, lymph nodes and mucosa-associated lymphatic tissue (MALT) they are supposed to attack and render harmless everything that is foreign.
Each lymphocyte is responsible for a different foreign structure. The foreign structures are also known as antigens. Each B-lymphocyte has a receptor on its surface. Upon contact with the specific antigen, the B-lymphocyte transforms into a plasma cell and produces antibodies against the foreign substance. These bind to the antigen and eliminate it.
The T-lymphocytes also have similar recognition mechanisms. If a pathogen penetrates a cell, it presents part of the pathogen on its surface. The T-lymphocytes recognize this so-called antigen presentation. This activates them and differentiates them. The resulting T killer cells destroy the diseased cell, T helper cells attract additional immune cells to provide support and regulatory T cells prevent excessive immune reactions.
The imprinting organs actually ensure that lymphocytes, which are imprinted on the body's own structures, do not get into the body's circulation. Such lymphocytes should change their blueprint for the receptor. If this does not succeed, they are eliminated with the help of apoptosis. In a healthy body, only lymphocytes that are tolerant of the body's own structures circulate.
In autoimmune diseases, this tolerance is lost. The body's own antigens are not recognized by the lymphocytes. They react to these substances as if they were foreign substances. However, the exact mechanism by which autoimmunity develops has not yet been sufficiently clarified. Two different causes are discussed: On the one hand, it is possible that there are foreign antigens that are similar to the body's own antigens. Thus, the antibodies that are produced during an immune response also unintentionally damage the body's own antigens. On the other hand, it is conceivable that autoreactive cells, i.e. cells that also react to their own tissue, are not eliminated during the lymphocyte imprinting, but are retained. It is not known why the immune system is directed against components of the thyroid in one person and against components of the pancreas in other people.
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A well-known autoimmune disease is multiple sclerosis (MS). Here the immune system reacts to the covering of nerve fibers. The insulating layers of the nerve fibers, the myelin sheaths, are destroyed in the process. The disease is characterized by lesions of the axons. These are found throughout the central nervous system, but are often located in the area of the optic nerve and the brain stem.
In the majority of patients, the disease begins between the ages of twenties and forty. Early symptoms of MS are visual disturbances, unsteady gait, numbness or tingling in the arms and legs, and dizziness.
The disease often progresses in phases. At first the symptoms recede completely. As the disease progresses, disabilities often persist. Often the relapsing course changes into a progressive stage. Multiple sclerosis is incurable.
Another autoimmune disease is lupus erythematosus (LE). The systemic disease belongs to the collagenoses. A high titer of autoantibodies is characteristic. These are directed against the DNA. Lupus can be divided into different sub-forms. Systemic PE mostly affects women between the ages of twenties and forty. The autoantibodies and the resulting immune complexes cause tissue damage and thus cause the typical dermatological clinical picture.
This shape runs in batches and is characterized by the so-called butterfly erythema on the face. There are also joint diseases, pleurisy, pericarditis and kidney damage. The nervous system is also involved. The subacute cutaneous form is much milder. This is where red, flaky skin appearances on parts of the body exposed to the sun. The disease cannot be cured. Severe cases require high-dose cortisone or chemotherapy.
The chronic inflammatory bowel diseases ulcerative colitis and Crohn's disease are also autoimmune diseases. Both diseases lead to inflammation of the intestines. In Crohn's disease, the inflammation can occur throughout the digestive tract. The small intestine, large intestine and esophagus are preferably affected. Ulcerative colitis almost exclusively affects the large intestine. The patients of both diseases suffer from abdominal pain, diarrhea, fever, weight loss, loss of appetite, nausea and vomiting.
In about half of all patients there are also manifestations outside the intestine. In Graves' disease, the antibodies are directed against thyroid tissue. The antibodies produced attack the thyroid's TSH receptors. TSH, the thyroid stimulating hormone, is produced in the pituitary gland and stimulates the thyroid gland to produce thyroid hormones. The effect of the antibodies on the receptor is similar to that of TSH. This leads to an overproduction of the thyroid hormones T3 and T4. The result is an overactive thyroid (hyperthyroidism) with a classic trio of symptoms of a rapid heartbeat, goiter and protruding eyeballs (exophthalmos).
