T-bet binds to the proximal site of the IFN-γ promoter in patients with aplastic anemia. (A) Nuclear extracts from healthy controls and patients were examined in EMSA experiments using an oligonucleotide that spans from –75 to –45 bp on the human IFN-γ promoter site (proximal IFN-γ promoter site). Unstimulated extracts from aplastic anemia patients revealed increased T-bet binding. In patients with lower T-bet protein levels (patient no. 1, Figure 1B) this binding was induced after stimulation. No binding could be detected in unstimulated nuclear extracts from healthy controls. (B) The binding observed in unstimulated extracts from aplastic anemia patients was decreased in supershift experiments using a T-bet mAb, indicating binding specificity.