forsinkettype

Forsinkettype, known in English as type IV hypersensitivity, is a form of immune reaction mediated primarily by T lymphocytes rather than antibodies. It produces a delayed inflammatory response after exposure to an antigen, typically developing within 24 to 72 hours.

The mechanism involves a sensitization phase during the first exposure, when antigen-presenting cells present the stimulus to T cells. Upon re-exposure, CD4+ T helper 1 cells (and sometimes CD8+ cytotoxic T cells) release cytokines such as IFN-γ and TNF-α, which recruit and activate macrophages. The ensuing inflammatory environment can cause tissue damage and, in some settings, granuloma formation as macrophages aggregate around persistent antigens.

Clinical examples illustrate the concept. The tuberculin skin test (PPD) and many forms of allergic contact dermatitis (for instance, to nickel or poison ivy) are classic forskinket-type reactions. This pathway also contributes to granulomatous conditions seen with certain infections and non-infectious diseases, including tuberculosis and sarcoidosis, where organized macrophage collections form in response to persistent antigenic stimulation.

Diagnosis relies on clinical history and supportive tests, such as patch testing for contact dermatitis or delayed-type skin tests. Management focuses on removing the offending antigen and reducing inflammation, commonly with topical corticosteroids; in more severe or chronic cases, systemic immunomodulatory therapies may be considered.