Which of the following is the preformed toxin involved in mechanism of allergic rhinitis -

Ans. is 'a' i.e., Histamine Examples of immediate hypersensitivity reaction includeAnaphylaxis (drugs, bee sting, food)Bronchial asthmaAllergic, rhinitis/ sinusitis (hay fever)Food allergieso Mediators of Immediate Hypersensitivity: Mast cell activation leads to degranulation, with the discharge of preformed (primary) mediators that are stored in the granules, and de novo synthesis and release of secondary mediators, including lipid products and cytokines.o Preformed (Primary) Mediators. Mediators contained within mast cel! granules are the first to be released and can be divided into three categories:Vasoactive amines - Histamine (most important). Enzymes - Neutral proteases (chymase, tryptase) and several acid hydrolases.# Proteoglycans-Heparin and chondroitin sulfate.# Lipid Mediators-Arachidonic acid-derived products: leukotrienes and prostaglandins# Leukotrienes-Leukotrienes C4 and D4 are the most potent vasoactive and spasmogenic agents known. They are several thousand times more active than histamine in increasing vascular permeability and causing bronchial smooth muscle contraction. Leukotriene B4 is highly chemotactic for neutrophils, eosinophils, and monocytes.Prostaglandin D2Platelet-activating factor (PAF).o Cytokines - Mast cells are sources of many cytokines, which may play an important role at several stages of immediate hypersensitivity reactions. The cytokines include: TNF, IL-1, and chemokines, which promote leukocyte recruitment (typical of the late-phase reaction); IL-4. which amplifies the TH2 response.