Which of the following is not true regarding IgE antibodies?

Ans. d. May cross the placenta and fix complement (Ref: Ananthanarayan 9/e p98)IgE doesn't fix the complement and doesn't cross the placenta.IgE:Exhibits unique properties such as heat lability (inactivated at 56degC in one hour)Affinity 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 tracts.It is responsible for the anaphylactic type of hypersensitivityThe 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 infectionsIgE 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 9/e 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 hour)Affinity 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 Ig75-85%(commonest)Q7-15%5-10%0.3%0.019%(least) Q2. Molecular weight (kDa)150(Lightest) Q160950(Heaviest) Q1751903. Usual molecular formMonomer QMonomerDimer QPentamer QMonomerMonomer4. SubclassesG1, G2, G3, G4(four) QA1, A2 (Two) QNoneNoneNone5. Serum half life (Days)23 Q(Maximum half life)6532.5 Q(Shortest)6. Complement activationClassical Q(++)Alternate QClassical Q(+++)QAlternate QNone7. Placental transport+----8. Present in milk++---9. Selective secretion by seromucous glands-+---10. Heat stability (56degC)++++-