Abstract
Flow cytometry (FCM) is a useful tool to detect phenotypes of blood cells. Paroxysmal nocturnal hemoglobinuria (PNH), an acquired hematopoietic stem cell disorder, is characterized by its affected blood cells defective in the expression of glycosyl phosphatidylinositol (GPI)-anchored proteins. GPI-anchored membrane proteins on the red blood cells (RBC) include two major complement-regulatory membrane proteins, CD55 and CD59. The most characteristic clinical feature of PNH, intravascular hemolysis of PNH-affected RBC, is induced by the complement-mediated lysis of CD55- and CD59-negative PNH-RBC. In addition to the RBC membrane defects, leukocytes and platelets are also defective in the expression of GPI-anchored proteins, because of the PNH mutations occurred in the pluripotential hematopoietic stem cells. The GPI-anchored proteins with cell-lineage specificity, CD16b in neutrophils and CD14 in monocytes, are also shown to be deficient in PNH by FCM. We recently applied FCM to the demonstration of CD59-deficient populations in reticulocytes. FCM is also useful to demonstrate RBC membrane alteration in the aspects of lipids associated with the procoagulant pathophysiology in PNH.
