Reticulocyte-gated flow cytometric analysis of red blood cells in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic stem cell disorder characterized by the deficiency of glycosyl phosphatidylinositol (GPI)-anchored proteins in the affected blood cell membranes. Analysis of blood cells by flow cytometry is useful to identify the affected blood cells with PNH-specific phenotypes. Because PNH-affected red blood cells (RBC) have shortened life-spans in the circulation, ratios of PNH-affected populations analyzed by flow cytometry in whole RBC are lower than those in PNH-affected erythropoiesis. We developed a reticulocyte-gated 2-color flow cytometry of RBC and revealed that the percentages of PNH-affected, CD59--populations in reticulocytes were higher than in whole RBC in patients with PNH. A serial analysis of a patient with PNH who underwent peripheral blood stem cell transplantation confirmed the usefulness of this method to evaluate PNH-affected RBC populations with high sensitivity; ie, the presence of CD59- reticulocytes in the circulation could be a sensitive marker for PNH-affected erythropoiesis.