Überempfindlichkeit

Überempfindlichkeit, also known as hypersensitivity, refers to an exaggerated or inappropriate immune response to an antigen that would be tolerated in a normal immune system. This can lead to tissue damage and disease. Hypersensitivity reactions are classified into four main types, categorized by Gell and Coombs. Type I hypersensitivity, also called immediate hypersensitivity or allergy, is mediated by IgE antibodies and involves the release of histamine and other inflammatory mediators upon re-exposure to an allergen. Examples include anaphylaxis, asthma, and hives. Type II hypersensitivity involves antibodies (IgG or IgM) directed against cell-surface or extracellular matrix antigens, leading to cell lysis, inflammation, or functional disturbances. Examples include autoimmune hemolytic anemia and Goodpasture's syndrome. Type III hypersensitivity, or immune complex-mediated hypersensitivity, occurs when soluble antigens react with antibodies, forming immune complexes that deposit in tissues and activate complement, causing inflammation. Serum sickness and certain autoimmune diseases like lupus erythematosus are examples. Type IV hypersensitivity, also known as delayed-type hypersensitivity or T-cell mediated hypersensitivity, is mediated by T lymphocytes rather than antibodies. It typically develops 24-72 hours after exposure to an antigen. Contact dermatitis and the tuberculin reaction are classic examples. The severity of hypersensitivity reactions can range from mild and localized to life-threatening and systemic. Diagnosis often involves a combination of clinical history, physical examination, and specific immunological tests. Treatment strategies aim to reduce the immune response, block the effects of mediators, or remove the offending antigen.