Figure 7. NK cell apoptosis by PAK is dependent on ROS.

(A) NK92 cells were infected with PAK at MOI of 10⁻² for 18 h. Then the cells were treated with dichlorodihydrofluorescein diacetate (DCFDA) for 30 min. Intracellular ROS production was monitored fluorometrically by oxidation of DCFDA. Data are representative histograms from three individual experiments. (B) NK92 cells were pretreated with MAP kinase inhibitors for 1 h followed by PAK infection for 16 h. Intracellular ROS production was measured by FACS analysis. (C) Effect of ROS on MAP kinase activation. NK92 cells were treated with H₂O₂ (50 µM) for indicated time. MAP kinase activation was monitored by immunoblot analysis using antibodies against phospho-p44/p42, p38, and JNK. (D) NK92 cells were pretreated with diphenyleneiodonium chloride (DPI) at the designated concentration for 1 h, and then infected with PAK at a MOI of 300. Apoptosis was analyzed by flow cytometry at 6 h post-infection with Annexin-V staining. Assays were performed in triplicate: error bars indicate±SD (*p<0.05, **p<0.01).