ENRICHMENT OF HEMATOPOIETIC PROGENITOR CELLS FROM THE MARROW OF PATIENTS WITH MYELODYSPLASIA

Myeloid and erythroid progenitors from myelodysplastic marrows have been separated from accessory cell populations likely to influence their in-vitro growth. Myeloid colony-forming cells were enriched 23-fold and erythroid progenitors 5.sbd.7-fold but, in both cases, retained their abnormal growth characteristics. After enrichment and removal of lymphocytes and monocytes, erythroid burst formation became markedly more dependent on the addition of 5637 bladder carcinoma conditioned medium as an exogenous source of haemopoietic growth factors. This suggests that lymphocytes and monocytes usually support erythropoiesis in cultures of myelodysplastic marrow and demonstrates that erythroid burst-forming progenitor cells from myelodysplastic patients can respond to these populations in vitro. Haemopoietic failure in myelodysplasia appears to result from a defect within the preleukaemic clonogenic cell, rather than from an aberration in exogenous factors. The procedure outlined here can be used as a first step towards the isolation of these abnormal progenitors.