What is the name of the necrotizing reaction observed at the site of the second injection when horse serum is first administered intravenously into a rabbit and then injected into the skin two to three weeks later?

Explanation

The Arthus phenomenon is a localized necrotizing hypersensitivity reaction that occurs when an antigen is injected into the skin of an individual previously sensitized by intravenous exposure to the same antigen. This reaction results from the formation of immune complexes at the injection site, causing inflammation and tissue damage. It differs from atopy, anaphylaxis, and serum sickness, which have distinct pathophysiological mechanisms.