Multilineage potential of CD34⁺CD38⁻ progenitor cells surviving in response to Tpo. CD34⁺CD38⁻ BM cells were seeded at a density of 1 cell per well in Terasaki plates and incubated in serum-depleted medium supplemented with Tpo for 116 hours before a strong proliferative cocktail of cytokines was added (containing IL-1, IL-3, IL-6, G-CSF, GM-CSF, CSF-1, FL, KL, Epo, and Tpo). After an additional 10 days of incubation at 37°C and 5% CO₂ in air, clones containing 10 or more cells were picked and transferred to methylcellulose cultures containing the same cytokine cocktail and incubated for a final 12 to 14 days. Cultures were scored for the presence or absence of GM, E, or mixed (GM/E) colonies. Cultures containing both GM and E colonies or mixed (GM/E) colonies were collectively grouped as Mix. To confirm colony phenotypes, individual colonies were picked, transferred to glass slides with a jet air stream, dried, fixed, Giemsa-stained, and examined by microscopy. An average of 21 wells were picked per group and replated in methylcellulose, of which an average of 13 formed colonies. The results represent the means (+SEM) of a total of five individual experiments.