THE PROPERDIN SYSTEM AND IMMUNITY. IV. THE HEMOLYSIS OF ERYTHROCYTES FROM PATIENTS WITH PAROXYSMAL NOCTURNAL HEMOGLOBINURIA 1

Abstract
Similarities between the factors required for the hemolysis of erythrocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH) and the factors comprising the properdin system are pointed out. Removal of properdin from serum renders it inactive for PNH hemolysis but not for immune hemolysis; readdition of properdin restores hemolytic activity. A relationship exists between the PNH hemolytic activity and properdin titers of sera. The ability of thrombin to affect PNH hemolysis may be due to the presence of properdin in samples of thrombin. The PNH hemolytic system of serum includes properdin, Mg and factors indistinguishable from complement.