Requirement for Properdin in Hemolysis of Human Erythrocytes Treated with Tannic Acid.

Summary 1) The hemolysis of normal human erythrocytes exposed to appropriate dilutions of tannic acid by human serum, requires the properdin system, which consists of properdin, complement, and magnesium. 2) Similarities and differences are pointed out between the properties and mechanism of hemolysis of tannic-acid-treated cells and erythrocytes from patients with paroxysmal nocturnal hemoglobinuria. 3) While the hemolysis of TA cells is suitable for the assay of purified properdin it is not reliable for the quantitative measurement of properdin in serum.