Overgevoeligheidsreacties: immuuncomplexreacties

Type III hypersensitivity, or immune complex reactions, result from antibodies binding to soluble antigens in the circulation, forming immune complexes. These circulating complexes then activate the complement system, triggering an inflammatory cascade.

When not efficiently cleared by the immune system, these complexes can deposit in the walls of blood vessels and tissues. This deposition recruits complement proteins and neutrophils, which manifests as serum sickness. It is a systemic immune response characterized by fever, rash, joint pain, and lymph node enlargement. It can happen in response to some commonly used antibiotics, among other things.

Another example of the type III hypersensitivity is the Arthus reaction. In previously sensitized individuals, exposure to antigens, like those from insect bites or fungal spore inhalation, can lead to the formation of large quantities of antigen–antibody complexes at the exposure site. This triggers a localized inflammatory response, resulting in redness, swelling, and tissue damage at the site.