Hemolysin Titration Based on Fixation of the Activated First Component of Complement: Evidence That One Molecule of Hemolysin Suffices to Sensitize an Erythrocyte
Summary: A new method for titrating hemolysin (A) is described. This method is based on the fixation by sensitized erythrocytes (EA) of the activated first component of complement (C′1a). The quantity of C′1a fixed by EA is determined by the ability of the EAC′1a to convert EAC′4 to EAC′1a,4. Hemolysin titrations by this new method have yielded data which are consistent with the hypothesis that one molecule of hemolysin suffices to sensitize an erythrocyte to the action of complement. When conventional titrations are performed under conditions where complement concentration does not affect the rate of lysis, data are obtained which support the view that one molecule of A produces a sensitized site on an erythrocyte.