Globulins are a diverse group of globular proteins found in blood plasma, comprising the alpha, beta and gamma fractions. They perform transport, immune and enzymatic functions and are distinct from the major plasma protein albumin.
Explanation
Plasma globulins are synthesized primarily by the liver and lymphoid tissue and can be separated by serum protein electrophoresis into alpha1, alpha2, beta and gamma bands. Alpha and beta globulins include transport proteins such as transferrin (iron transport), ceruloplasmin (copper transport), lipoproteins and enzyme inhibitors like alpha1-antitrypsin. They help maintain osmotic balance and carry hormones, metals and lipids through the circulation. Gamma globulins consist largely of immunoglobulins produced by B lymphocytes and plasma cells; these antibodies recognize and neutralize pathogens. Complement proteins, fibrinogen and certain clotting factors are also classified within globulins. Abnormal globulin levels can indicate disease: decreased gamma globulins occur in immunodeficiency, while increased levels are seen in chronic infections and plasma cell disorders such as multiple myeloma. Measurement of the albumin/globulin ratio is part of routine blood chemistry to assess liver and immune system function. Therapeutically, pooled human gamma globulin preparations are administered to provide passive immunity for individuals with antibody deficiencies.
Notable examples and facts
Alpha1-antitrypsin is an alpha globulin that inhibits neutrophil elastase; deficiency leads to emphysema and liver disease. elastase; deficiency leads to emphysema and liver disease. Transferrin, a beta globulin, transports iron and increases in iron deficiency anemia. Complement component C3, part of the innate immune system, is a beta globulin that opsonizes pathogens. Intravenous immunoglobulin (IVIG) therapy uses purified gamma globulins from pooled human serum to treat immune deficiencies and autoimmune diseases. Serum protein electrophoresis displaying a monoclonal “M spike” in the gamma region is characteristic of multiple myeloma.
Globulins collectively support transport, immunity and homeostasis in the circulatory system. Monitoring their concentrations provides insight into liver function, nutritional status and immune health.
Related Terms: Albumin, Immunoglobulin, Serum, Complement, Alpha globulin