Gammaglobulin

Charlotte Cunningham-Rundles, Department of Medicine and Pediatrics, Mount Sinai Medical Center, New York, NY, USA

Copyright © 1998 Elsevier Ltd. All Rights Reserved.

Gammaglobulin is a somewhat ambiguous term that still remains in common usage despite attempts to substitute 'immunoglobulin' in its place. In general terms, 'gammaglobulin' is a class of plasma proteins composed almost entirely of immunoglobulins (Igs), the proteins that function as antibodies. These plasma proteins are characterized by a very slow electrophoretic mobility in an alkaline buffer (Figure 1). 'Gammaglobulin' is also used as a clinical name, given to the immunoglobulin concentrates that are given parenterally to humans for immuno-prophylaxis against infectious disease, or for passive antibody replacement in humoral immunodeficiency disease.

The term 'gammaglobulin' has deep roots in the history of immunology and the evolution of immunoprophylaxis. The globulins were those proteins found to be soluble in dilute salt solution and precipitated at half saturation with ammonium sulfate, in distinction from the albumins, which require complete saturation with ammonium sulfate in order to precipitate them. Typical globulins were first believed to be insoluble in water in the absence of salt, but the globulins were later divided into two parts, the 'euglobulins' (mostly IgM) of which this feature is true, and the 'pseudoglobulins' (mostly IgG) which dissolve even in the absence of salt.

The electrophoretic separation of plasma into components of various charge, including the a, and y fractions, was first performed by Tiselius, who gave these names to the fractions in 1937. Two years later, Tiselius and Kabat identified antibody in the slowest moving proteins, the y fraction. Ethanol precipitation of the gammaglobulin proteins from pooled human serum, introduced in 1944 by Cohn and colleagues, became a standard method of isolating almost pure gammaglobulin (called fraction II). Figure 2 shows the plasma fraction scheme that was developed. After fraction II was found to contain most of the antibodies present in serum, it became an important prophylactic agent given parenterally to humans to protect against certain infectious diseases. Later, this immunoglobulin concentrate was introduced as a means of reconstitution for immuno-deficient patients who had no antibody production of their own.

Numerous physical and chemical studies on the properties of the gammaglobulin molecules were

Figure 1 Serum protein electrophoresis. Typical conditions for separation on paper or other suitable support include a 0.1 m sodium diethylbarbital buffer (pH 8.6, potential gradient 6 V cm 1) over a time period of 250 min.

Figure 1 Serum protein electrophoresis. Typical conditions for separation on paper or other suitable support include a 0.1 m sodium diethylbarbital buffer (pH 8.6, potential gradient 6 V cm 1) over a time period of 250 min.

Blood

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