CFU-C and LTC-IC in CD34⁺CD40⁺ and CD34⁺CD40⁻ blood cells. Purified CD34⁺CD40⁺ and CD34⁺CD40⁻ blood cells were tested for their clonogenic activity in semisolid medium, and the results show the mean number ± SEM of colonies/10⁴ cells plated according to the scale on the left side of the figure (n = 3 experiments) and for their content of LTC-IC. The results show the mean number ± SEM of LTC-IC/10⁴ cells plated according to the scale on the right side of the figure (n = 3 experiments). Differences in the number of colony units between CD34⁺CD40⁺ and CD34⁺CD40⁻ blood cells are not statistically significant.