The gamma fraction in birds contains most of the immunoproteins, including IgA, IgE, IgM and IgG. In some species, nonimmunoglobulin proteins, including transferrin, complement and fibrinogen, are found within the gamma globulin fraction.

Gamma globulins increase with ongoing antigenic stimulation, often from infectious agents. Broad increases (polyclonal gammopathies) in gamma globulins occur with acute or chronic inflammation, infection, chronic hepatitis and immune-mediated disorders. Sharp increases (monoclonal gammopathies) occur with tumors of the reticuloendothelial system and plasma cell dyscrasias. Deficiencies can occur with immunodeficiency states, blood loss, overwhelming infection, protein-losing GI diseases and severe inanition. The half-life of gamma globulins in birds is relatively short.

Panhypoproteinemia, which occurs when both albumin and globulins are decreased, may occur with severe inanition or malnutrition, severe hepatic insufficiency, overwhelming infection, protein-losing states (especially GI or kidney), external blood loss, or blood loss into the body cavity.

There are some instances when the electrophoretic pattern may be difficult to interpret. Avian neonates and juveniles likely show age-related differences in serum proteins, but this has not been fully investigated. Thus, caution is advised when interpreting electrophoretic patterns of young birds. In some psittacine species, a monoclonal spike may be present in the beta fraction during periods of egg-laying, when there is transport of egg proteins to the ovary. This increase in an egg-laying hen has been attributed to transferrin, and to increases in estrogen-induced yolk protein precursors, vitellogenin and lipoproteins. In raptors, there are normal variations in electrophoresis patterns that differ from those found in psittacines.

A unique electrophoretic pattern has been reported during acute chlamydiosis. Typically, there is a moderate to severe hypoalbuminemia, mild to moderate elevation in beta globulins,and moderate to severe hypergammaglobulinemia. In chronic chlamydiosis, there may be no changes in the inflammatory proteins, or only a mild hyperbetaglobulinemia. In mycotic diseases, especially aspergillosis, an increase in the beta fraction is seen during the acute phase. There may be beta or gamma globulin elevations during the chronic phase of aspergillosis. Eventually, birds chronically infected with aspergillus may lose the inflammatory protein response altogether, becoming hypoproteinemic. Mycobacterial infections may show increases in either beta or gamma globulins, whereas sarcocystis infections usually show an elevation in both beta and gamma fractions. Birds with hepatitis or nephritis often show a decrease in albumin and increases in beta globulins. Gross hemolysis may show a severely restricted (usually gamma) spike composed of hemoproteins that can be misinterpreted as being clinically important.

This newsletter was contributed by Marge Wissman DVM, Dipl ABVP (Avian Practice) and Robin Lane DVM, Dipl ABVP (Avian Practice).