Expression of bcl-xL by normal and IMF megakaryocytes. (A) depicts a representative flow cytometric analysis of bcl-xL expression by normal and IMF CD41⁺ cells after 3 days of secondary culture (day 18). Percentages represent the percentage of CD41⁺ cells expressing Bcl-xL. (B) shows the decay of bcl-xL expression in the percentage of CD41⁺ cells present in normal, IMF, and PV cultures. After 11 days of culture, there was a marked decline in the expression of bcl-xL in the normal CD41⁺ cells, while the expression of bcl-xL remained persistently elevated until day 18 in the IMF and PV CD41⁺ cells and then decreased after that. A significant difference in the expression of bcl-xL was observed between the normal and IMF-cultured cells (P < .01) (n = 5 and 7, respectively). Values are shown as the mean ± SD. (C) represents the expression of bcl-xL by CD41⁺ cells derived from CD34⁺ cells isolated from patients with IMF. The overexpression of bcl-xL was independent of JAK2 617V>F mutational status (P > .05). Values are shown as the mean ± SD.