Type IV Hypersensitivity

**Semantic type:** Disease or Syndrome

**Definition:** Delayed hypersensitivity reaction (DTH) - type IV reaction, an inflammatory response that develops 24 to 72 hours after exposure to an antigen that the immune system recognizes as foreign. DTH is mediated by T cells rather than by antibodies. Th1 cells produce interferon gamma, interleukin (IL)-2, and tumor necrosis factor-beta and promote a cell-mediated immune response.

**Synonyms:** - DTH - Delayed Hypersensitivity Reaction - Delayed-Type Hypersensitivity - Delayed-Type Hypersensitivity Response - Type 4 Hypersensitivity Reaction - Type 4 Hypersensitivity Reaction - Type IV Hypersensitivity Reaction - Type IV Hypersensitivity Reaction - delayed-type hypersensitivity response