Fig 4.

Preincubating bovine macrophages with LKT increases the trapping and killing of M. haemolytica by METs. Bovine macrophages (10⁵) were incubated with 10⁷ fluorescein-labeled M. haemolytica cells (A) or unlabeled M. haemolytica cells (B) for 60, 120, or 180 min. Similarly, LKT-treated (0.5 U LKT for 30 min) or untreated macrophages were incubated for 60 min with 10⁷ fluorescein-labeled M. haemolytica cells (C) or 10⁷ unlabeled M. haemolytica cells (D). Untreated macrophages were used as controls. Additional controls included macrophages incubated with M. haemolytica and 180 U DNase I. Bacterial trapping was estimated by fluorescence using an automated plate reader. Bacterial survival was estimated by plating serial dilutions of lysates on TSA–5% sheep RBC plates. Data represent the mean ± SEM of 5 independent experiments. a, P < 0.05 compared to macrophages incubated with M. haemolytica for 180 min; b, P < 0.05 compared to untreated macrophages; c, P < 0.05 compared to macrophages treated with LKT alone.