Mechanical Fragility of Erythrocytes from Patients with Paroxysmal Hemoglobinuria. ∗

Abstract

Summary

1. As pH of blood samples from 6 normal subjects was decreased, susceptibility of normal erythrocytes to mechanical trauma or their mechanical fragility was increased. 2. MF determinations on PNH and normal erythrocytes were done at various values of pH including the range for optimum complement activity in normal serum and it was found that mechanical trauma did not contribute to hemolysis of normal or PNH erythrocytes even though the PNH hemolytic mechanism was active. 3. It is postulated that increased red cell volume due to a shift of C1-, HCO₃- and H₂0 into the erythrocyte, may be the mchanism of increasing spheroidicity of the erythrocyte and the MF as a function of decreasing values of pH.

Conclusion. 1. MF of erythrocytes of the PNH patient in an active properdin system does not differ from MF of the same erythrocytes in an inactive properdin-complement system, nor does the MF of these erythrocytes differ from that of normal erythrocytes at values of pH between 8.0 and 5.9. 2. The hemolytic system of PNH, which requires properdin, complement and Mg^{+ +}, does not enhance susceptibility of PNH erythrocyte to hemolysis by mechanical trauma in vitro. Hemolysis of PNH and normal erythrocytes attributable to mechanical trauma increases progressively as pH of blood decreases until a critical point (pH 6.0-6.2) where MF rises rapidlv.