Characterization of circulating erythrocytes from myelodysplastic patients treated with recombinant human erythropoietin.

Age-density fractionation, in-vitro erythrophagocytosis, and enumeration of membrane-bound antibodies were monitored for circulating red blood cells (RBC) from five anemic patients with myelodysplastic syndromes (MDS), in relation to administration of recombinant human erythropoietin (rhEPO). The density distribution patterns of erythrocytes from the patients prior to treatment were in accordance with their inability to produce compensating levels of circulating RBC. The complete response of one patient to rhEPO and partial responses of two other patients were accompanied by shifts to larger proportions of low density (young) RBC. In vitro phagocytosis of density-fractionated RBC from the complete responder was similar to those of age-matched non-anemic donors. Elevated erythrophagocytosis prior to rhEPO administration was observed for the partial responders and further increased during treatment in one, suggesting the stimulation of abnormal progenitors producing highly defective erythrocytes. There was no correlation between levels of erythrophagocytosis and RBC membrane-bound immunoglobulins in this group of patients. Our findings suggest that density distribution analysis of circulating RBC coupled with in vitro erythrophagocytosis may provide useful predictive tools for selecting potential responders to rhEPO administration among anemic MDS patients.