Fetal hemoglobin in paroxysmal nocturnal hemoglobinuria (PNH): evidence for derivation of HbF-containing erythrocytes (F cells) from the PNH clone as well as from normal hemopoietic stem cell lines

The cellular distribution of HbF was studied in nine patients with paroxysmal nocturnal hemoglobinuria (PNH) by measuring the level of HbF and determining the number of HbF-containing red cells (F cells) in whole blood and in the population of normal cells obtained after immune lysis of the abnormal erythrocytes. The amounts of HbF and the F cell frequencies found in the normal red cells were strikingly similar to the values seen in whole blood. The observed frequencies of F cells in normal cells best fitted those expected under the assumption that the F cells arise equally from normal hemopoietic stem cells and from the stem cells with the PNH defect. Since PNH appears to be a clonal hemopoietic stem cell disorder, this evidence argues against a derivation of F cells from distinct pluripotent stem cell lines.