Abstract
TWO inborn errors of the complement system of man have been well documented: hereditary deficiency of the serum inhibitor of the activated first component of complement (C′1a) and hereditary deficiency of the second component of complement (C′2). To appreciate both the nature of the inborn errors and their possible consequences, it is necessary to review very briefly certain basic aspects of the complement system.The sequence in which the components of complement act in immune hemolysis is depicted in Figure 1; this scheme is based on studies by many investigators using both guinea pig and human complement (reviewed by Rapp and . . .