Fig 2.

SpeB activities in human plasma and in the presence of activated neutrophils. (A) Activated SpeB was incubated in human plasma with (■) or without (□) 2 mM DTT for 0 to 120 min at 37°C. Enzymatic activity measurements were initiated by addition of the chromogenic substrate BPFA. SpeB activity remains stable in human plasma over time. The negative control is plasma only (◆). (B) SpeB activity in the presence of PMA-activated or nonactivated PMNs. PMN activation was monitored by measurements of extracellular ROS (black bars). SpeB activity (gray bars) against the chromogenic substrate BPFA is inhibited by ROS. **, P < 0.01 by Student's t test. Presence of activated and nonactivated SpeB inhibits PMA-induced extracellular ROS. *, P < 0.05 by Student's t test.