Merck, I8260-10MG, IgM from human serum

There are five immunoglobulin classes in humans. Out of these, immunoglobulin M (IgM) is a high molecular weight protein that has five or six subunits. IgM monomers are made of two heavy chains and two light chains connected by a disulfide bond. Human serum shows low concentration of IgM monomers. It has a high carbohydrate content of about 12%. It is the first immunoglobulin produced by neonates. IgM antibodies are present as pentamers in the serum and are produced in response to antigens. IgM from human serum is purified from normal human serum by precipitation and gel filtration techniques. The immunoglobulin is determined to be atleast 95% pure by HPLC procedures.