Effects of p13 in primary T cells. Freshly isolated PBMCs were electroporated with plasmids expressing mt-GFP, wild-type p13-GFP, or mutant p13-GFP. Resting or mitogen-activated PBMCs were cultured for 3 days and then analyzed by flow cytometry to assess activation by measuring the percentage of activated (CD38+) in the transfected (GFP-positive) and untransfected populations. T cells were identified by staining with anti–CD3 antibody. (A) Expression of WT-p13 resulted in a highly significant activation of resting T cells. This effect was lost with mutant p13 (A) and in the presence of ROS scavengers (B). In contrast no effect of p13 was observed in mitogen-activated T cells (E-F), or in non-T cells (C,D,G,H). Reported are mean values and error bars from 5 independent experiments (in the absence of NAC) and 3 independent experiments (in the presence of NAC). Indicated P values were calculated with the Mann-Whitney test.