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Autoimmune conditions: causes, symptoms, diagnosis, treatment
Last reviewed: 23.04.2024
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In autoimmune conditions, antibodies to endogenous antigens are produced. Cells carrying an antibody, like any cells with foreign particles on the surface, activate the complement system, which leads to tissue damage. Sometimes complexes of antigen-antibody (hypersensitivity reaction of type III) are involved in the mechanism of damage. Specific autoimmune lesions are discussed in other chapters of this publication.
[Causes of autoimmune conditions
There are several mechanisms of autoimmune damage.
Autoantigens can acquire immunogenic properties due to chemical, physical or biological changes. Certain chemicals are combined with body proteins, making them immunogenic (as in contact dermatitis). Drugs can induce some autoimmune processes through covalent binding to serum or tissue proteins. Photosensitivity is an example of physically induced auto-allergy: ultraviolet alters the skin proteins to which the patient develops an allergy. In animal models, it has been shown that the persistence of the RNA of a virus that is associated with host tissues alters biha autoantigens, resulting in autoallergic disorders such as SLE.
Antibodies produced in response to a foreign antigen may cross-react with normal autoantigens (cross-reactivity between streptococcal M protein and protein structures of human cardiac muscle tissue).
Normally, autoimmune reactions are suppressed by specific regulatory T lymphocytes. Deficiency of regulatory T-lymphocytes can be accompanied or be the result of any of the above mechanisms. Anti-idiotypic antibodies (antibodies to the antigen-binding site of other antibodies) may interfere with the regulation of antibody activity.
A certain role is played by genetic factors. In relatives of patients with autoimmune disorders, the same type of autoantibodies is often detected, the frequency of autoimmune disorders is higher in odnoyaytsevye than in frog twins. Women suffer from autoimmune diseases more often than men. Genetic factors determine the predisposition to autoimmune conditions. In predisposed patients, external factors can provoke the disease (so, certain medications can provoke hemolytic anemia in patients with G6PD deficiency).