MARKEDLY HIGH POPULATION OF AFFECTED RETICULOCYTES NEGATIVE FOR DECAY-ACCELERATING FACTOR AND CD59 IN PAROXYSMAL-NOCTURNAL HEMOGLOBINURIA

Paroxysmal nocturnal hemoglobinuria (PNH) blood cells lack glycosylpho sphatidylinositol-anchored membrane proteins such as decay-acceleratin g factor (DAF) and CD59. This lack is of diagnostic value in PNH. Beca use reticulocytes in PNH are not yet well characterized, we analyzed r eticulocytes obtained from 12 patients with PNH and from 5 healthy vol unteers by two-color flow cytometry with a membrane-permeable fluoresc ent dye, thiazole orange, to identify reticulocytes and monoclonal ant ibodies to DAF and CD59. Healthy individuals had no affected cells. In all patients, the population of affected reticulocytes negative for D AF and CD59 was markedly higher than the population of affected erythr ocytes. Moreover, the population of affected erythrocytes became obvio usly low in patients who received transfusions and suffered from hemol ytic precipitation, whereas the population of affected reticulocytes w as unchanged. The persistently high population of affected reticulocyt es, despite cytolytic exclusion and an inherently short lifetime, migh t possibly be explained by relative reticulocytosis caused by an anemi a-induced feedback stimulation of erythropoiesis in PNH. Thus, affecte d reticulocytes could be a reliable marker for the diagnosis of PNH an d for the evaluation of erythropoiesis by PNH stem cell. (C) 1995 by T he American Society of Hematology.