T cell proliferation and apoptosis in Parp-1+/+ and Parp-1-/- T cells. (A) Splenic T cells from Parp-1+/+ (white bars) and Parp-1-/- (black bars) were stimulated with plate-bound anti-CD3 mAb alone or in combination with anti-CD28 mAb for 24 h, 48 h and 72 h. Proliferation was measured by 3H-thymidine uptake during the last 12 h of culture. Data are representative of 3 separate experiments carried on in triplicate. Results represent the mean value ± SD. *P < 0.05 in t-test. (B) Apoptosis of T cells from Parp-1+/+ (white bars) and Parp-1-/- (black bars) was detected by FITC-Annexin-V and Propidium iodide staining and flow cytometric analysis at 24 hours after stimulation. Results represent the mean value ± SD of two independent experiments.