Effects of IFN-γ, AA, and melittin on the NSE activity and the NBT reduction. HL-60 cells were cultured for 5 days in the presence of IFN-γ (2,000 U/mL), AA (10 μmol/L), melittin (500 ng/mL) or the combination of IFN-γ (2,000 U/mL) and AA (10 μmol/L) and the combination of IFN-γ (2,000 U/mL) and melittin (500 ng/mL). The cells were harvested and stained for α-NSE activity (A) and for the NBT reducing ability (B) The data (means ± SD) are expressed as a percentage of the control level obtained from three independent experiments assayed in duplicate. * Significantly different (P < .05, Student's t-test) from controls.