Hypersensitivities

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Hypersensitivities

Hypersensitivities (pronounced: hi-per-sen-si-tiv-i-tees) are a set of conditions where the immune system reacts abnormally to a foreign substance. The term originates from the Greek words "hyper" meaning over, and "sensitivity" meaning a state of being sensitive.

Types of Hypersensitivities

There are four types of hypersensitivities, each with its own unique characteristics and triggers:

  1. Type I Hypersensitivity (also known as immediate hypersensitivity) typically occurs within minutes of exposure to an allergen and can lead to conditions such as asthma, allergic rhinitis, and anaphylaxis.
  2. Type II Hypersensitivity (or cytotoxic hypersensitivity) involves the destruction of host cells by the immune system, often leading to conditions like hemolytic anemia and Goodpasture syndrome.
  3. Type III Hypersensitivity (or immune complex hypersensitivity) is characterized by the formation of immune complexes that can deposit in various tissues, causing inflammation and damage.
  4. Type IV Hypersensitivity (or delayed-type hypersensitivity) is mediated by T cells and typically takes 48-72 hours to develop. It is involved in many autoimmune and infectious diseases, including tuberculosis and contact dermatitis.

Related Terms

  • Allergy: A hypersensitivity reaction to a particular allergen; symptoms can vary greatly in severity.
  • Autoimmunity: A misdirected immune response that occurs when the immune system goes awry and attacks the body itself.
  • Immunology: The branch of medicine and biology concerned with immunity.
  • Antigen: A substance that induces a immune response in the body, especially the production of antibodies.

See Also

External links

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