Overfølsomhedssygdomme

Overfølsomhedssygdomme, also known as hypersensitivity diseases, encompass a group of conditions where the immune system reacts inappropriately to a substance or process, leading to damage or dysfunction. These reactions are essentially exaggerated or misdirected immune responses. They are broadly categorized into four main types, often referred to as Gell and Coombs classification.

Type I hypersensitivity, or immediate hypersensitivity, involves IgE antibodies and is responsible for common allergies such as hay fever, asthma, and anaphylaxis. Upon exposure to an allergen, IgE antibodies bind to mast cells, triggering the release of histamine and other inflammatory mediators.

Type II hypersensitivity, or cytotoxic hypersensitivity, involves antibodies (IgG or IgM) that target antigens on the surface of cells or in tissues. This can lead to cell destruction. Examples include autoimmune hemolytic anemia and Rh disease.

Type III hypersensitivity, or immune complex hypersensitivity, arises when soluble antigens bind to antibodies, forming immune complexes. These complexes can deposit in tissues, activating the complement system and leading to inflammation. Examples include serum sickness and lupus nephritis.

Type IV hypersensitivity, or delayed hypersensitivity, is mediated by T lymphocytes rather than antibodies. It typically develops over 24 to 72 hours after exposure to an antigen. Contact dermatitis, such as poison ivy rash, and the tuberculin reaction are classic examples.

The development of overfølsomhedssygdomme is influenced by a combination of genetic predisposition and environmental factors. Diagnosis often involves clinical assessment, skin testing, blood tests to detect specific antibodies or immune cells, and sometimes biopsy. Treatment strategies aim to reduce the immune response, manage symptoms, and prevent further exposure to triggers.