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What is Ahur reaction is what type of hypersensitivity reaction and explain in detail?
Ref Robbins 8/p205.,7/e p215, 9/e p207 Local Immune Complex Disease A model of local immune complex diseases is the Ahus reaction, in which an area of tissue necrosis appears as a result of acute immune complex vasculitis. The reaction is produced experimentally by injecting an antigen into the skin of a previously immunized animal (i.e., pre-formed antibodies against the antigen are already present in the circulation). Because of the initial antibody excess, immune complexes are formed as the antigen diffuses into the vas- cular wall; these are precipitated at the site of injection and trigger the same inflammatory reaction and histologic appearance as in systemic immune complex disease. Ahus lesions evolve over a few hours and reach a peak 4 to 10 hours after injection, when the injection site develops visible edema with severe hemorrhage, occasionally fol- lowed by ulceration.