LDH release from F. tularensis- infected cells. Culture supernatants of infected J774 cells were assayed for LDH activity at 24 h with a MOI of 200, 500, or 1,000. The activity was expressed as a percentage of the level of uninfected lysed cells. The value of uninfected cells at 24 h was 14.6 ± 1.6%. Means and SEM of six replicate wells are shown. The asterisks indicate that the LDH levels were significantly different to those of LVS-infected cells at the same time point as determined by a two-sided t-test with equal variance (**: P < 0.01, ***: P < 0.001).