RT Book, Section A1 Yazdany, Jinoos A1 Manno, Rebecca A1 Hellmann, David B. A1 Imboden Jr., John B. A2 Papadakis, Maxine A. A2 McPhee, Stephen J. A2 Rabow, Michael W. SR Print(0) ID 1175804308 T1 Immediate Hypersensitivity T2 Current Medical Diagnosis & Treatment 2021 YR 2021 FD 2021 PB McGraw-Hill Education PP New York, NY SN 9781260469868 LK accessmedicine.mhmedical.com/content.aspx?aid=1175804308 RD 2023/02/05 AB IgE antibodies occupy receptor sites on mast cells. Within minutes after exposure to the allergen, a multivalent antigen links adjacent IgE molecules, activating and degranulating mast cells. Clinical manifestations can be explained by the effects of released mediators on target end organs. Both preformed and newly generated mediators cause vasodilation and permeability changes, visceral smooth muscle contraction, mucous secretory gland stimulation, vascular permeability, and tissue inflammation. Arachidonic acid metabolites, cytokines, and other mediators (such as chemoattractants) induce a late-phase inflammatory response that appears several hours later in affected tissues when antigen exposure is continuous (eg, pollen) or chronic.