Abnormal Immunoglobulins

Abnormal Immunoglobulins

Abnormal immunoglobulins are other structurally similar proteins that are found in serum in certain pathological condi-tions, such as multiple myeloma, heavy chain disease, and cryo-globulinemia and sometimes in healthy individuals also.

Multiple myeloma: Bence-Jones (BJ) proteins were theearliest abnormal proteins described in 1847 that were found in patients with multiple myeloma. These proteins are the light chains of immunoglobulins, hence occur as either or forms. In a patient, it may occur as either or but never in both the forms. BJ proteins have a peculiar property of coagulating at 60°C and redissolving again at a higher tem-perature of 80°C.

In multiple myeloma, plasma cells synthesizing IgG, IgA, IgD, or IgE are affected. Myeloma involving IgM-producing plasma cells is known as Waldenström’s macroglobulinemia. This condition is characterized by excessive production of the respective myeloma proteins (M proteins) and that of their light chains (BJ proteins).

The study of myeloma proteins led to a great advancement in our understanding of immunoglobulin function. These “single” or “monoclonal” antibodies obtained from the sera of patients with multiple myeloma were used in many of the serologic and biochemical studies of the 1950s and 1960s. They remained the major source of homogeneous immuno-globulins until the development of the hybridoma in 1974. The serologists injected them into animals and produced antisera that were used to study some of the basic properties of antibod-ies. For example, the immune sera were absorbed with other myeloma proteins and were used to identify isotypic, allotypic, and idiotypic specificities.

Heavy chain disease: Heavy chain disease is a different disor-der, which is a lymphoid neoplasia, characterized by an excess production of heavy chains of the immunoglobulins.

Cryoglobulinemia: Cryoglobulinemia is a condition charac-terized by presence of cryoglobulins in blood. The condition may not be always associated with disease but is often found in patients with macroglobulinemia, systemic lupus erythe-matosus, and myelomas. Most cryoglobulins consist of either IgG or IgM or their mixed precipitates. In cryoglobulinemia, serum from patient precipitates on cooling and redissolves on warming.