TLR9-engaged CD4 T cells show increased DNA repair activity. (A) CD4 T lymphocytes were treated as described in Figure 1. Briefly, after activation and TLR9 ligand treatment CD4 T cells were irradiated or not. Comet analysis was conducted 30 minutes after irradiation. Representative images of DNA comet formation 30 minutes after irradiation are shown. (B) The levels of IR-induced DSB DNA damage (using neutral pH conditions that specifically detect DSB), at the indicated time points after IR are shown as tail moment, percent tail DNA, and tail intensity. Data are the means (± SD, n > 150 cells per condition). (C) Thirty minutes after IR the levels of DSBs were measured using the comet assay in cells treated with Chk1 and Chk2 inhibitors, UCN-01, DBH, or inhibitors of ATM, ATR and related protein kinases, wortmannin. The data shown are representative of at least 2 experiments, each showing identical results. P values for all 3 graphs in panel B were determined by use of 2-way analysis of variance using data acquired between 20 and 90 minutes after IR; *P < .05. Groups with asterisks represent groups that reached statistical differences as compared with irradiated, TLR9-stimulated cells.