EARLY CIRCULATING ERYTHROID PROGENITOR CELLS AND EXPRESSION OF ERYTHROPOIETIN RECEPTORS IN SICKLE-CELL DISEASE

The ability of circulating progenitor cells from 22 patients with sick le cell disease (SCD) to develop erythroid colonies was studied in vit ro in the presence or absence of growth factors (5637-CM and erythropo ietin). In both conditions, SCD patients presented significantly highe r numbers of circulating burst-forming unit-erythroid (BFU-E/5x10(5)MN C) when compared to control subjects. The study of the expression of e rythropoietin receptors revealed an increased level in SCD patients. M oreover, there was a correlation between both stimulated and autocrine (without stimulus) BFU-E and the expression of erythropoietin recepto rs. These results are of particular interest since they indicate that the phenomenon of spontaneous BFU-E-derived colonies observed in SCD p atients may be due to an increased expression of erythropoietin recept ors.