RELATIONSHIP BETWEEN THE PHENOTYPES OF CIRCULATING ERYTHROCYTES AND CULTURED ERYTHROBLASTS IN PAROXYSMAL-NOCTURNAL HEMOGLOBINURIA

To investigate erythropoiesis in paroxysmal nocturnal hemoglobinuria ( PNH), we studied the expression of glycosylphosphatidylinositol (GPI)- anchored membrane proteins on circulating erythrocytes and erythroblas ts obtained by erythropoietic cell culture in nine patients with this disease. One-color and two-color flow cytometric analyses were perform ed using monoclonal antibodies for decay-accelerating factor (DAF) and /or CD59/membrane attack complex-inhibitory factor (MACIF). In additio n, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end -labeling (TUNEL) analysis was performed to assess apoptosis of erythr oblasts from six patients. On flow cytometric analysis, cases 1 to 6 h ad positive and negative erythrocyte populations, case 7 intermediate and negative populations, case 8 positive, intermediate, and negative populations, and case 9 a single double negative population. In additi on, cases 1 to 6 and 8 had positive, intermediate, and negative erythr oblast populations, while cases 7 and 9 had intermediate and negative populations. The percentage of double-negative erythrocytes showed a s ignificant correlation with that of double-negative erythroblasts (r = .741, P < .05). In seven of nine patients, more erythroblasts than er ythrocytes were negative for the two membrane proteins. Also, some pat ients with an intermediate population of erythrocytes did not necessar ily show an increase of PNH II erythroblasts. Apoptosis of PNH erythro blasts was also detected, but the percentage of apoptotic cells in PNH patients showed no difference from that in healthy volunteers. These findings suggest that the final phenotype of mature erythrocytes in PN H is determined during maturation from erythroblasts to erythrocytes b y the disappearance or persistence of PNH II erythroblasts. In additio n, PNH erythroblasts in vitro may be partly lost by apoptosis, but apo ptosis does not play an important role in determining GPI-linked prote in expression. (C) 1997 by The American Society of Hematology.