Anti-IgM antibodies are protein reagents that detect specific antigens. The IgM antigen is another term for the human protein CD40 ligand, encoded by the CD40LG gene. The protein is a reported cytokine that acts as a ligand to CD40/TNFRSF5. Canonically, it has an amino acid length of 261 residues and a mass of 29.3 kilodaltons. Its subcellular localization is in the cell membrane and is secreted. It is expressed in the skin, rectum, lymph node, colon, and bone marrow. The IgM protein is a member of the Tumor necrosis factor protein family. Other alias names for IgM include CD154, CD40L, and HIGM1. Over 3800 citations in the literature describe the use of IgM antibodies in research. ELISA is a widely used application for these antibodies. Western Blot and Immunohistochemistry are also common applications.