FIG 7.

Serine proteases, especially neutrophil elastase, contribute to the UT12-mediated clearing of P. aeruginosa. Neutrophils were incubated with rabbit serum-opsonized P. aeruginosa, and survival was assessed following a 45-min incubation. The percentage of bacterial survival was calculated based on viable counts (CFU per milliliter) relative to those for no-neutrophil controls. Shown are the results obtained using neutrophils treated with the oxidative burst inhibitor DPI (A), the serine protease elastase inhibitor AEBSF, CHYM, or the neutrophil elastase inhibitor (B) before the OPH assay. The UT12-mediated reduction of viable bacterial counts was abolished by elastase inhibitor pretreatment, suggesting that the nonoxidative pathway, specifically involving neutrophil elastase, might be important for UT12-mediated bactericidal activation. An asterisk indicates a significant difference (*, P < 0.05) from non-UT12-treated neutrophils.