Studies in vivo and in vitro on an abnormality in the metabolism of C3 in a patient with increased susceptibility to infection

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Abstract

In a patient with increased susceptibility to infection, lowered serum C3 concentration, and continuously circulating C3b, it was shown that purified 125I-labeled C3 was converted to labeled C3b shortly after intravenous administration. The fractional catabolic rate of C3 was approximately five times normal at 10% of the plasma pool per hr. The synthesis rate and pool distribution of C3 were normal. Despite this evidence of C3 instability in vivo, no accelerated inactivation of C3 was found in vitro. Similarly, no free proteolytic activity could be detected in the patient's serum, and serum concentrations of known protease inhibitors were normal.

Authors

Chester A. Alper, Neil Abramson, Richard B. Johnston Jr., James H. Jandl, Fred S. Rosen