Globulins

Globulins are a group of serum proteins that, along with albumin, make up most of the plasma protein content. They are traditionally separated by electrophoresis into alpha, beta, and gamma fractions, with each fraction containing multiple proteins that perform different physiological roles.

Alpha globulins include transport and enzyme-regulating proteins such as alpha-1 antitrypsin and ceruloplasmin. Beta globulins include transferrin and various components of the complement system. Gamma globulins are antibodies, or immunoglobulins, produced mainly by plasma cells and forming the humoral portion of the immune response.

Functions of globulins are diverse. They participate in transport of minerals and hormones, metal binding, and enzyme inhibition. Immunoglobulins provide targeted immune defense by recognizing and neutralizing pathogens. Some globulins are components of the complement system, which helps mediate inflammation and pathogen clearance. Fibrinogen, a key coagulation factor, is a plasma protein but is not classified as a globulin.

Clinical relevance of globulins lies in their measurement and interpretation. Serum protein electrophoresis quantifies the albumin and globulin fractions and the albumin-to-globulin ratio. Hypergammaglobulinemia can occur with chronic infections, autoimmune diseases, and liver disorders, while hypogammaglobulinemia may indicate immunodeficiency. A monoclonal band or spike in the gamma region (monoclonal gammopathy) can indicate disorders such as multiple myeloma or monoclonal gammopathy of undetermined significance.