This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Anaphylaxis refers to 
Select and explain. 
A. The severe reaction following primary injection of protein solutions, B. The state of immunity developed by repeated injections of any foreign substance, C. The severe reaction resulting from sensitive to common allergens, D. The severe reaction following re-injection of protein solution in a sensitized animal
D: The severe reaction following re-injection of protein solution in a sensitized animal
Answer: D: The severe reaction following re-injection of protein solution in a sensitized animal 
Explanation: The general mechanism of immediate hypersensitivity involves a series of steps. An antigen induces the formation of IgE antibody, which binds firmly by its Fc poion to high-affinity IgE receptors on mast cells, basophils, and possibly eosinophils.Sometime later, an individual experiences a second exposure to the same antigen. This second exposure results in the cross-linking of the cell-bound IgE molecules and the release of pharmacologically active mediators.Jawetz 27e pg: 145