| Type III hypersensitivity | |
|---|---|
 | |
| Immune complex | |
| Specialty | Immunology  |
Type III hypersensitivity, in the Gell and Coombs classification of allergic reactions, occurs when there is accumulation of immune complexes (antigen-antibody complexes) that have not been adequately cleared by innate immune cells, giving rise to an inflammatory response and attraction of leukocytes. There are three steps that lead to this response.[1] The first step is immune complex formation, which involves the binding of antigens to antibodies to form mobile immune complexes. The second step is immune complex deposition, during which the complexes leave the plasma and are deposited into tissues. Finally, the third step is the inflammatory reaction, during which the classical pathway is activated and macrophages and neutrophils are recruited to the affected tissues. Such reactions may progress to immune complex diseases.
- ^ Usman, Norina; Annamaraju, Pavan (2021), "Type III Hypersensitivity Reaction", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 32644548, retrieved 2021-11-26