FIG. 3.

Tulathromycin induces apoptosis in bovine neutrophils in a time- and concentration-dependent manner in vitro. (A) Levels of apoptotic mono-/oligonucleosomes in neutrophils incubated with tulathromycin (50 μg/ml to 2 mg/ml) for 0.5 h and 2.0 h were measured using a cell death ELISA. Values were calculated as absorbance ratios versus values measured in neutrophils from controls incubated with HBSS (control), arbitrarily set to 1.0. (B) Fluorescent staining of apoptotic neutrophils after 0.5 h of incubation with HBSS (control) or tulathromycin (TUL; 2 mg/ml), as determined by annexin V-FITC fluorescent staining of externalized phosphatidyl serine. Values are means ± standard errors of the means. n = 6/group. * and #, P < 0.05 versus control.