Concentrations of hPF4 released into the media during megakaryocyte differentiation of human CD34⁺ cells. (A) hPF4 level changes in the media of human CD34⁺ cells grown in TPO only in serum-free media. n = 2 separate studies done in duplicate. Mean + 1 SD shown. (B) Analysis of percentage of CD41⁺-derived megakaryocytes at the same day points of culture as in panel A for 1 of the studies.