Fig. 5.
iNOS activity in human NK cells. NOS activity was determined by monitoring of [14C] L-citrulline produced per milligram of cellular protein per minute. NK cells were stimulated with IL-12 (5 U/mL) or/and TNF (20 ng/mL) for 48 hours, and then cell lysates were prepared and tested for their NOS catalytic activity by measuring their capacity to convert radiolabeled arginine into citrulline, as described in Materials and Methods. Results are expressed as the mean ± SD of three representative experiments. Significance of inhibition was assessed by the Student’st-test after comparison of the values obtained with IL-12 or/and TNF + AMG, with the corresponding values obtained in each experiment with IL-12 or/and TNF (**P < .01; *P< .05).