Human Complement

Abstract

Human complement is composed of 4 components similar to, but not entirely identical with, the components of guinea-pig complement. The 3 component (C[image]3) is the only component which is effectively mutally substitutive in human and guinea-pig complement systems. This is the only component that has features suggestive of enzymic nature. Human C[image]l has been purified by (NH4)2SO4 precipitation and a phosphate buffer extraction. It is characterized as a euglobulin with an electrophoretic mobility of 2.9 X 10-5 in veronal buffer of pH 7.8 and ionic strength 0.1. Evidence has been obtained to show that the bactericidal action of human serum against Vibrio comma is a result of the joint action of complement and antibody; and that this bactericidal effect is destroyed by inactivation of any one of the 4 components of complement. The bactericidal action is restored to a specifically inactivated complement by the addition to it of the particular component which it lacks. The bactericidal action of whole human complement against this vibrio can be fortified by addition of the end-piece (pH-5.4-0.02 supemate) of human complement. Fixations of whole human complement and specifically inactivated human complements to viable sensitized V. comma have been investigated. From whole human complement nearly all of the C[image]3 activity is removed during fixation and only small amts. of the activities of the other 3 components are removed. However, sufficient amts. of the components are fixed so as to cause the destruction of the vibrios.