Final answer:
Type III hypersensitivity is an immune reaction characterized by the formation of immune complexes that deposit on tissues and blood vessels, leading to inflammation and tissue destruction. It occurs when there is an excess of antibodies and a low concentration of antigen. This type of hypersensitivity can affect various body sites and is associated with diseases like systemic lupus erythematosus.
Step-by-step explanation:
Type III hypersensitivity is an immune response characterized by the inflammatory reaction induced by the formation of immune complexes and their deposition in tissues and blood vessels. This type of hypersensitivity occurs when there is an excess of antibodies, primarily IgG, coupled with a relatively low concentration of antigen, resulting in the formation of small immune complexes that deposit on the surface of blood vessels or tissues. This immune complex accumulation leads to a cascade of inflammatory events and can cause tissue destruction in various body sites.