FIG 4.

Kyn treatment inhibits the protection from Fas-mediated apoptosis provided by IL-2 and involves ROS production. (A) (Bottom) IL-2-induced pSTAT5 level on memory CD4 T cells in response to various Kyn concentrations. The percent inhibition of IL-2 signaling is indicated for each Kyn concentration. (Top) Representative histograms. (B) ROS expression by memory CD4 T cells in the presence or absence of 5 μM Kyn. We also stimulated CD4 T cells with increasing concentrations of H₂O₂. (C) CD4 T cells were preincubated with H₂O₂ for 1 h, stimulated with IL-2 for 15 min, and then collected to determine pSTAT5 levels in memory cells. (D) After 24 h of Kyn and/or NAC treatment, CD4 T cells were stimulated with IL-2 and pSTAT5 levels in memory cells were assessed. (E) Protection from Fas-mediated apoptosis by IL-2 in memory CD4 T cells in the presence or absence of Kyn and/or NAC. In panels A to E, data are for 5 subjects in each group. *, 0.05 > P > 0.01; **, 0.01 > P > 0.001; ***, P < 0.001.