IL-3 INCREASES MARROW AND PERIPHERAL ERYTHROID PRECURSORS IN CHRONIC PURE RED-CELL APLASIA PRESENTING IN CHILDHOOD

In most patients with Diamond-Blackfan anaemia (DBA) the addition of IL-3 to in vitro cultures increases the number of erythroid progenitors. However, a small proportion of patients show an erythroid response to in vivo administration of IL3. We treated two adult patients with corticosteroid-refractory DBA, who had shown a clear in vitro erythroid response to IL-3, with increasing doses of IL-3 (from 2.5 to 10 mu g/kg/d) by subcutaneous infections for 7 and 9 weeks. Monitoring of marrow and circulating progenitors showed a sustained elevation of BFU-E and CFU-E as well as an increase of other progenitors and CD34(+) cells during therapy. However, this effect did not translate into a clear clinical response, although transfusion requirements decreased transiently in one patient. This report shows that a sustained elevation of erythroid progenitors induced by in vivo IL-3 administration may not translate into an increase of mature red cells production in DBA patients.