Kinetics of apoptosis induction in resistant and susceptible <i>Mycobacterium bovis</i>–infected bovine macrophages, expressed as percentage (mean ± SD) of cells showing chromatin condensation after infection.

aMacrophages were pre-cultured with or without LPS for 18 h then infected with BCG or M. bovis field strain for 4 h, washed and cultured again for indicated times and then stained with propidium iodide. Two hundred macrophages were analyzed per slide in triplicate cultures and those with chromatin condensation were counted. Results are representative of two independent experiments with macrophages of three susceptible (S) and three resistant (R) cattle. *Significant differences (P<0.05) are among phenotypes.