Ex vivo expansion of megakaryocyte progenitor cells (CFU-Mk). CD34⁺ cells cultured in IL-1,6,11,S with or without TPO. Aliquots evaluated at indicated time points for the presence of CFU-Mk. The averages of three replicate cultures were determined for each cytokine combination, for each time point. Fold-increase values are mean ± SEM of the averaged (triplicate) values (n = 3). (▾), CFU-Mk expansion in 1,6,11,S; (•), CFU-Mk expansion in IL-1,6,11,S,T.