Immunoglobulins (Ig) are critical components of the immune system and play a major role in eliciting the body's immune response against pathogens. Five heavy-chain isotypes (IgA, IgD, IgE, IgG, and IgM) mediate specific biological functions, including responses to pathogens and immunological diseases such as allergies and autoimmune disorders. IgA has two subclasses (IgA1 and IgA2) and exists in both monomeric and dimeric forms. It is approximately 15% of the total serum Ig content. Secretory IgA is a dimer that provides the primary defense against localized infections. High levels of IgA are often found in samples from subjects with chronic infections such as cirrhotic liver disease. IgG, a monomer, is the dominant immunoglobulin class present in serum. Increased IgG is commonly seen in samples from subjects with humoral immunodeficiencies, autoimmune diseases, liver diseases, chronic inflammatory diseases, haematological disorders, infections, and lymphoid malignancies. IgM is a pentamer that comprises approximately 10% of serum immunoglobulin content. IgM level is often increased in samples from subjects with infectious diseases including primary biliary cirrhosis, infectious mononucleosis, cytomegalovirus infection, and tuberculosis. This kit provides the assay-specific components for the quantitative determination of IgA, IgG, and IgM in human, cynomolgus monkey, and rhesus monkey sera samples.