<prompt> Highest molecular weight immunoglobulins areIgGIgAIgMIgD  <response>: Ref: Ananthanarayan and Panikers, 8th ed. pg. 100Immunoglobulins and their salient featuresImmuno-globulinsSalient featuresIgG Most abundant Ig, makes as about 80 Marker of chronic infection Only Ig that can cross placentaIgA 2nd most abundant, 10-13 Found in glandular secretion like saliva, tear, ileum, and mucosal secretion like bronchial secretionIgM 5-8 of total Ig; aka pentameric Ig - has highest molecular weight First Ig to be synthesized by fetus 20 weeks AOG Marker of acute infectionIgD Present mostly intravascular Serve as recognition receptor for antigensIgE Mostly extravascular in distribution Highly elevated levels in case of type-I HPS reaction Produced chiefly in the linings of respiratory and intestinal tractsImmunoglobulin and their effective valencyAntibodyEffective valency IgM5 IgG2 IgD2 IgE2 IgA2,4 Ig having maximum molecular weight: IgM First antibody produced by newborn: IgM All immunoglobulins are heat stable except: IgE Ig present in breast milk: IgA Ig with maximum half-life: IgG Ig with minimum half-life: IgE Ig having maximum serum concentration: IgG Ig having least serum concentration: IgE 