IgE is the least abundant immunoglobulin in plasma, found at a concentration of less that 0.6 micrograms/ml of normal plasma. Elevated IgE levels are found in patients experiencing severe allergic reactions and parasitic infections. In a myeloma condition, IgE is produced by a single clone of plasma cells. The structure of myeloma IgE, however, is normal, and the immunoglobulin purified from a myeloma source is a useful protein for studying immunoglobulin behavior. The affinity purified IgE r