Growth factor responsiveness was unchanged following SCF administration. Results are shown for G-CSF (•) and SCF (○) titration curves examining d14 GM-CFC in (A) bone marrow at baseline and (B) after 5 days of growth factor treatment (SCF 10 μg/kg/d plus G-CSF ). Similar results were obtained for 4 individuals and for cells analyzed at day 12 of study (data not shown).