FACTORS CONTROLLING SERUM GAMMA-GLOBULIN CONCENTRATION.

Both synthetic and catabolic processes determine the serum gamma-globulin level. The rate of gamma-globulin synthesis appears to be the primary factor determining the amount of serum gamma-globulin. Increase of gamma-globulin synthesis (as may occur following immunization or development of plasma cell tumor) elevates the serum gamma-globulin level. This, in turn, accelerates the fractional rate of gamma-globulin catabolism. The change in catabolic rate reduces the dimensions of the serum change from that which would occur if synthesis alone determined the serum gamma-globulin level. The present studies indicate the existence of a homeostatic mechanism controlling the rate of gamma-globulin catabolism. The mechanisms of gamma-globulin catabolism are specific and selective. Marked serum increase of other immunoglobulin components (beta(2A)-globulins and gamma(1)-macroglobulins) do not accelerate gamma-globulin catabolism. Similarly, serum albumin increases do not influence gamma-globulin catabolism. The site determining gamma-globulin catabolism is restricted to a part of the gamma-globulin molecule; i.e., on the F piece obtained by papain digestion and, by inference, on the H chains obtained by reduction and alkylation of gamma-globulin molecules.