Enterobacter cloacae leukotoxin: modulation of reactive oxidant species generated by neutrophils

A leukotoxin purified from Enterobacter cloacae culture by saline precipita tion, gel chromatography and HPLC was studied as a modulator of reactive ox idant species (ROS) produced by human neutrophils. Chemiluminescence showed that stimulation of ROS was achieved at a low leukotoxin concentration, bu t ROS production decreased when the toxin was applied at concentrations abo ve 30 mug/mL. Also, the addition of 100 mug toxin/ml significantly reduced the activating effect of phorbol myristate acetate (PMA) and low doses of t oxin did not produce an opposite effect toward the stimulation produced by PMA. Normal neutrophils showed a linear correlation between the inverse of ROS production and time, but the kinetic reaction changed when toxins were added to the cells and the ROS formation increased directly with time. Copy right (C) 2001 John Wiley & Sons, Ltd.