IgM is the first antibody generated in an immune response to an antigen. It is generally a pentamer with each of the five immunoglobulins linked together with disulfide bonds. In its pentamer form, it has a molecular mass of 970 kDa and 10 antigen binding sites (due to the large size of most antigens, not all binding sites can be filled simultaneously.  IgM antibodies account for approximately 5%-10% of all the antibody in the body.

This mAb is specific for the human IgM heavy chain. It does not cross-react with other immunoglobulin heavy chains, T-cells, monocytes, granulocytes, or erythrocytes. IgM antibody is useful in the identification of certain cancer types. Some tumors express a single heavy chain class. Demonstration of clonality in lymphoid infiltrates indicates that the infiltrate is clonal and therefore malignant.

Store the anti-IgM antibody at 2-8°C (with azide) or aliquot and store at -20°C or colder (without azide).