tBHQ increases HbF levels in primary human erythroid cells. Human CD34⁺ peripheral blood cells were treated with tBHQ during in vitro erythroid differentiation. At the end of differentiation on day 20, cells were lysed, and the proportions of HbA and HbF were determined by ion exchange HPLC. (A) Representative HPLC traces. Arrows indicate HbF peak. (B) Quantitation of HbF from 3 experiments. A total of 500nM 5-Aza was used as a positive control for HbF induction. Error bars represent ± 1 SEM. *P < .05.