Neutralization of ROS with MnTBAP abrogated active TGF-β and reduced CD25+Foxp3+ T cells. CD4+CD25- T cells were cultured with anti-CD3 and anti-CD28 antibodies in the presence or absence of MnTBAP (100 μM) for 3 and 5 days. The intracellular ROS production was determined by DHE staining. Active TGF-β in the supernatants was determined with ELISA. The intracellular Foxp3 protein was determined by FACS staining. A. A representative overlay of histograms of ROS in the cultured T cells with (+MnTBAP) and without (-MnTBAP) MnTBAP at days 3 and 5. The filled histograms were from unlabeled cells as negative control for DHE staining. The experiment was repeated three times with similar results. B. The values are shown as the Mean ± SD of active TGF-β1 in the culture supernatants at days 3 and 5 (n = 2). C. MnTBAP reduced CD25+Foxp3+ T cells. Each symbol represents one individual.