Type iii reaction

The type III reaction according to Coombs and Gell is based on the formation of antigen-antibody immune complexes. Triggers are aggregates of allergen (often drug) haptens + carrier protein and the antibodies or complexes induced thereby, which are composed exclusively of allergen-specific immunoglobulins. These can precipitate in the postcapillary venules and cause leukocytoclastic vasculitis. The sensitization phase lasts about 10 days, the effector phase until the clinical symptoms appear 2-5 days.

Serum sickness: In this case, an immune complex reaction occurs rapidly due to an excessive activation of the complement system. For example, after two parenteral administrations of protein components foreign to the species, massive and acute complement activation and leukocytoclasia occur due to the formation and deposition of circulating immune complexes.

Immune complex disease in autoimmunity: E.g., chronic polyarthritis(rheumatoid arthritis); lupus erythematosus, systemic; vasculitis, leukocytoclastic; polyarteritis; fibrosing alveolitis.

Immune complex disease due to sensitization to environmental antigens: e.g., exogenous allergic alveolitis (avian lung, farmer's lung, byssinosis, cotton fever).

1. Biedermann T (2018) Basic principles of allergy and intolerance reactions. In: Braun-Falco`s Dermatology, Venerology Allergology G. Plewig et al. (Hrsg) Springer Verlag S 449-450