CD34⁺flt3⁺BM and CB cells contain LTC-ICs. Sorted CD34⁺flt3⁺(▪) and CD34⁺flt3^-(□) cells were plated on established stroma layers (“Materials and methods”). Six weeks after coculture, all cells were transferred to methylcellulose cultures, and the numbers of colonies were scored after 14 days. Results are expressed as number of colonies per 500 cells. Data represent mean values (SEM) from 3 adult BM and 4 CB experiments, with 4 to 6 replicates in each group. Differences between BM and CB CD34⁺flt3⁺and CD34⁺flt3^-cells were not statistically significant.