What is the name of the rapid immune response where antigens bind to antibodies that are already fixed on mast cells and basophils?

Explanation

Type I hypersensitivity refers to an immediate allergic reaction that occurs when antigens interact with antibodies attached to the surface of mast cells and basophils. This triggers the release of histamine and other mediators, causing symptoms typical of allergic responses. Other types (II, III, IV) involve different mechanisms and timing.