Studies on the Mechanism of in Vitro Acid Hemolysis in Paroxysmal Nocturnal Hemoglobinuria

1. The mechanism of acid hemolysis of PNH erythrocytes appears to be a direct mechanism, with the production of an initial "hole" in the membrane sufficiently large to permit the direct egress of hemoglobin.

2. PNH erythrocytes react like normal red cells with rabbit antihuman red cell antibody and human or guinea pig C' at pH 7.2 to produce a membrane defect which is less than 32.5 Å in effective diffusion radius.

3. Inhibition of acid hemolysis of PNH erythrocytes by high molecular weight dextrans (Dextran 150) is also associated with inhibition of K⁺ loss, indicating inhibition of complement.