MPN mononuclear cells and CD34⁺ cells are resistant to suppression of colony formation by TNFα. (A) Effect of TNFα on colony formation by progenitor cells from MNC. MNC from MPN patients (n = 14) and normal controls (n = 5) were plated in methylcellulose media supplemented with SCF, IL-3, with 5 U/mL (left) or 0.5 U/mL (right) EPO and graded concentrations of TNFα (in triplicate). Colonies were enumerated at day 12. Colony formation in 0 ng/mL TNFα is normalized to 100%. (B) Effect of TNFα on colony formation from CD34⁺ cells. CD34⁺ cells from MPN (n = 16 for 10 ng/mL TNFα, n = 3 for 1 ng/mL TNFα) and normal controls (n = 6 for 10 ng/mL TNFα, n = 3 for 1 ng/mL TNFα) were plated in methylcellulose media supplemented with SCF, IL-3 and 5 U/mL EPO, with graded concentrations of TNFα (in triplicate).