IgG (7 S Gamma Globulin) Metabolism in Hypogammaglobulinemia: Studies in Patients with Defective Gamma Globulin Synthesis, Gastrointestinal Protein Loss, or Both*

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Abstract
The metabolism of gamma globulin (IgG) was studied in 7 patients with gastrointestinal protein loss, 9 patients with agammaglobulinemia, and 14 control subjects. There was a reduction in the serum concentration and total body pool size of IgG in 6 of the 7 patients with gastrointestinal protein loss, with markedly increased fractional catabolic rate for IgG in each. In general, the increase in the fractional catabolic rate over normal was quite comparable for albumin, IgG, and gamma macroglobulin (IgM) for a given patient, thus suggesting that there was bulk loss of plasma or material with a comparable protein composition into the intestinal tract. The IgG synthetic rate was normal, or slightly increased, in 6 of the patients and markedly increased only in the single patient with regional enteritis. This suggests that a reduced serum IgG concentration is not a potent stimulus for IgG synthesis and that other factors, such as exposure to antigens, are the major stimuli. The primary disorder in the patients with agammaglobulinemia was defect in gamma globulin synthesis. Two of the 9 patients developed associated gastrointestinal disorders with secondary gastrointestinal protein loss and short IgG and albumin survivals; 6 of the 7 remaining patients had a reduced fractional catabolic rate of IgG with a normal fractional catabolic rate of albumin. The pathogenesis of this reduced fractional catabolic rate of IgG in patients with agammaglobulinemia is discussed.