Inhibition of fMLF-induced superoxide anion generation by PID-Tat protein. Human neutrophils were incubated in the absence or presence of the following proteins: BSA, GFP-Tat, PID-Tat, PID L107F-Tat, or Rac2 T17N-Tat. fMLF (1 μM)–stimulated O₂^·- generation was measured in 3 to 5 × 10⁵ cells by chemiluminescence. (A) Cells were preincubated with buffer (□), 1 mg/mL bovine serum albumin (○), or 1 μM GFP-Tat (▴). (B) Cells were preincubated with 1 μM GFP-Tat (▵), PID L107F-Tat (□), PID-Tat (♦), or Rac2 T17N-Tat (*). (C) Cells were preincubated with 2 μM PID L107F-Tat (□), 0.5 μM PID-Tat (▴), 1 μM PID-Tat (▾), or 2 μM PID-Tat (♦). The arrow indicates addition of fMLF. The depicted graphs are representative of 3 separate experiments.