TNF selects for JAK2^V617F+ colony formation. Percentage of JAK2^V617F mutant colonies in the absence or presence of TNFα. Colonies were plucked from (A) 6 MNC starting material and (B) 6 CD34⁺ starting material from plates with 0 ng/mL and 10 ng/mL TNFα (at least 30 individual colonies per condition) and JAK2 mutational status was determined. Panels A and B represent different patients and are numbered arbitrarily. Mutational analysis of separated CFU-GM and BFU-E from these patients is provided in supplemental Figure 3.