<prompt> IgE receptor is present on:Mast cellPromonocyteB cellNK cell  <response>: Ans. a. Mast cell Ref: Ananthanarayan 9e p162, 163IgE receptor is present on Mast cell.IgE molecules are bound to surface receptors on mast cells and basophils. These cells carry; large number of such receptors called Fc ER receptors, analogous to TCR receptors on T cell surface. IgE molecules attach to these receptors by their Fc end. Following exposure to the shocking dose, the antigen molecules combine with the cell bound IgE, bridging the gap between adjacent antibody molecules. --Ananthanarayan 9e p162Upon activation, mast cells release various classes of mediators that are responsible for the immediate and late-phase reactions. ECF, eosinophil chemotactic factor: NCF. neutrophil chemotactic factor neither of these is biochemically defined; PAF, platelet-activating factor.IgEIgE molecules are bound to surface receptors on mast cells and basophilsQ.Exhibits unique properties such as heat lability inactivated at 56degC in one hourAffinity for the surface of tissue cells particularly mast cells of the same species homocytotropism.It mediates the Prausnitz-Kustner reaction.Normal serum contains only traces but greatly elevated levels are seen in atopic conditions type 1 allergic conditions such as asthma, hay fever and eczema.Children living in insanitary conditions, with a high load of intestinal parasites, have high serum levels of IgE.IgE is chiefly produced in the linings of the respiratory and intestinal tractsQ.It is responsible for the anaphylactic type of hypersensitivity QThe physiological role of IgE appears to be protection against pathogens by mast cell degranulation and release of inflammatory mediatorsIt is also believed to have a special role in defense against helminthic infectionsPropertyIgGIgAIgMIgDIgE1. Percentage of total serum Ig75-85commonestQ7-155-100.30.019least Q2. Molecular weight kDa150Lightest Q160950Heaviest Q1751903. Usual molecular formMonomer QMonomerDimer QPentamer QMonomerMonomer4. SubclassesG1, G2, G3, G4four QA1, A2 Two QNoneNoneNone5. Serum half life Days23 QMaximum half life6532.5 QShortest6. Complement activationClassical QAlternate QClassical QQAlternate QNone7. Placental transport---8. Present in milk---9. Selective secretion by seromucous glands----10. Heat stability 56degC- 