What is the Origin of Hypersensitivity?

The term is a compound of the Greek prefix hyper- (over or excessive) and "sensitivity," referring to the state of being reactive to a stimulus. It was originally conceptualized in the early 20th century to describe the phenomenon where a second exposure to an antigen caused a more severe reaction than the first. The classification system developed by Gell and Coombs categorized these reactions into four distinct types, providing a structural framework for modern immunopathology.

What is the Mechanism of Hypersensitivity?

The mechanism of hypersensitivity is categorized into four main types: Type I (Immediate), mediated by IgE antibodies and mast cell degranulation; Type II (Cytotoxic), involving IgG or IgM antibodies binding to cell surface antigens; Type III (Immune Complex), where antigen-antibody complexes deposit in tissues; and Type IV (Delayed), mediated by T lymphocytes rather than antibodies. Each mechanism involves a distinct cellular and molecular pathway, but all result in an overzealous immune attack that damages healthy host tissue.

Hypersensitivity ∞ Area

Hypersensitivity

Meaning

Hypersensitivity, in a broad clinical sense, describes an exaggerated or inappropriate immune response to an antigen that results in tissue damage and disease, extending beyond the normal protective immune function. This adverse reaction can manifest in various forms, including allergic reactions, autoimmune diseases, or contact dermatitis, depending on the specific immunological mechanism involved. Understanding the underlying type of hypersensitivity reaction is crucial for effective diagnosis and targeted therapeutic intervention.