Description_x000D_ General description_x000D_ Immunoglobulin M (IgM) is the major component of antibodies. It is the first antibody to be secreted during a primary antibody response, which is expressed in the human fetus. IgM is produced by B1 cells, which is found in blood._x000D_ Disclaimer_x000D_ Unless otherwise stated in our catalog or other company documentation accompanying the product(s), our products are intended for research use only and are not to be used for any other purpose, which includes but is not limited to, unauthorized commercial uses, in vitro diagnostic uses, ex vivo or in vivo therapeutic uses or any type of consumption or application to humans or animals._x000D_ Biochem/physiol Actions_x000D_ IgM antibodies are present as pentamers in the serum and are produced in response to antigens._x000D_ Immunoglobulin M (IgM) pentamer activates the classical pathway of complement activation and lysis of red blood cells. Monoclonal IgM antibodies provides protection against systemic infection and autoimmune diseases. It does not cross human placenta. IgM regulates B cell development.