Effect of different concentrations of TPO on the generation of CD41⁺cells in vitro. This figure represents the percentage of CD41⁺ cells generated in suspension culture from normal and IMF CD34⁺ cells in the presence of 100 ng/mL SCF and various concentrations of TPO (0-200 ng/mL) (n = 3) after 11 days of culture. In the absence of TPO, the percentage of CD41⁺ cells was significantly greater in cultures of IMF CD34⁺ cells compared with normal (P < .05). The addition of 5 ng/mL TPO resulted in a marked increase in the percentage of normal CD41⁺ cells (> 95% of the maximal output), while causing a far smaller increment in the percentage of CD41⁺ cells in the IMF samples (38% of the maximal output). A relative plateau in the percentage of CD41⁺ cells was observed at higher doses of TPO. The * indicates significant differences between the percent of normal CD41⁺ cells in normal and IMF cultures (P < .05). Values are shown as the mean ± SD.