TPO dose response of PMF MPL 1544 G>T and 1543 TG>AA and PMF JAK2 1849G>T (V617F) CD34⁺ cells compared with normal CD34⁺. CD34⁺ cells from PMF patients were cultured in Terazaki plate at 1 cell/well. For each TPO concentration (0, 0.01, 0.1, 0.2, 1, 5, 10, and 100 ng/mL), 120 cells were plated. Clones were counted at 10 days. The data represent the mean plus or minus SEM of 3 separate experiments performed in each group (PMF W515, n = 3; PMF JAK2 V617F, n = 3; and healthy controls, n = 3). *P < .05 compared with normal CD34⁺. The difference between PMF MPL W515L/K and PMF JAK2 V617F is not significant. The same TPO dose response was noticed for MPL W515L (n = 2) and MPL W515K (n = 1).