serum globulin

serum globulin

n.

A protein fraction of serum composed chiefly of antibodies.

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serum globulin

Etymology: L, serum, whey, globulus, small globe

one of a group of proteins in blood serum with antibody qualities. The various types of serum globulins, designated alpha, beta, and gamma, have different specific properties.

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globulin

a general term for proteins that are insoluble in water or highly concentrated salt solutions but soluble in moderately concentrated salt solutions. All plasma proteins except albumin and prealbumin are globulins. The plasma globulins can be separated into five fractions by serum protein electrophoresis (SPE). In order of decreasing electrophoretic mobility these fractions are the alpha₁, alpha₂, beta₁ and beta₂ globulins, and the gamma globulins.

The globulins include carrier proteins, which transport specific substances; acute phase reactants, which are involved in the inflammatory process; clotting factors; complement components; and immunoglobulins. Examples are transferrin, a beta₁ globulin that transports iron, and alpha₁-antitrypsin, an acute phase reactant that inhibits serum proteases. The gamma globulin fraction is almost entirely composed of immunoglobulins.

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accelerator globulin

a substance present in plasma, but not in serum, that functions in the formation of intrinsic and extrinsic thromboplastin; called also clotting factor V.

antihemophilic globulin (AHG)

clotting factor VIII.

antilymphocyte globulin (ALG)

a substance used as an immunosuppressive agent in organ transplantation, usually in combination with immunosuppressive drugs; it is the gamma globulin fraction of antilymphocyte serum.

immune globulin

a sterile solution containing antibodies normally present in blood, derived from donor animals, sometimes after hyperimmunization with certain microorganisms; used for passive immunization against some infectious diseases and in the treatment of gamma globulin deficiency.

serum globulin

the fraction of proteins precipitated from blood serum by half saturation with ammonium sulfate; the principal groups include the α-, β- and γ-globulins.