This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Which immunoglobulin is found scarce in human serum? \nSelect and explain. \nA. IgG, B. IgM, C. IgE, D. IgA', 'role': 'user'}, {'content': 'Answer: C \nExplanation: There are five classes of immunoglobulin (Ig): IgG, IgM, IgA, IgD and IgE.\nIn normal serum, about 80% is IgG, 15% is IgA, 5% is IgM, 0.2% is IgD and a trace is IgE.\nIgE is mainly produced in the linings of respiratory and intestinal tracts. Serum contains only traces (a few nanograms per ml).\xa0\nIt is mostly distributed extravascularly.\nIt is also referred to as reagins.\xa0\nMolecular weight is 1,90,000 (8S molecule).\xa0\nHalf life is 2-3 days.\nIt resembles IgG in structure.\nIt is heat labile (inactivated at 56°C in one hour) whereas other immunoglobulins are heat stable.\nIt has affinity for surface of tissue cells, particularly mast cells of the same\xa0 species (homocytotropism).\nIgE mediates type I hypersensitivity (atopic) reaction.This is responsible for asthma, hay fever, eczema and Prausnitz-Kustner (PK) reaction.\nHigh level of IgE in serum is also seen in children with a high load of intestinal parasitism.\xa0\nIt cannot cross the placental barrier or fix the complement.\nIgE is responsible for anaphylactic type of reaction.\xa0\nIt may play some unidentified role in defence against intestinal parasitic infections\n\nRef : textbook of microbiology, C P Baveja, 5th edition , Pg no:102', 'role': 'assistant'}]