FIG. 1.

Nonlinear effects of IFN-γ exposure on bacterial binding. MH-S cells were seeded and grown in media (changed daily) for 7 days, with varying durations of exposure to IFN-γ (25 ng/mL/day) lasting between 0 and 6 days before inoculation with the type II Streptococcus pneumoniae D39. Bacterial binding was measured as the difference between total bacterial colony forming units (CFUs) internalized and bound (bacteria released from MH-S cells with saponin treatment only) versus bacterial CFUs internalized (gentamicin protection assay to kill extracellular-bound cells followed by saponin treatment to release internalized bacteria). Bacterial CFUs reflect bacteria bound per macrophage (ie, bound CFU/viable MH-S cells). Binding in each condition are then reported as a proportion of the mean CFUs bound to IFN-γ unexposed control cells. Each bar represents pooled results from 3 independent experiments and each experiment examining 3 distinct wells for each condition for a total of 9 data points per condition (depicted as gray filled circles). Boxes represent the interquartile range (IQR) and whiskers extend to 1.5× IQR on either side. Horizontal lines represent the median and the connecting line connects the means. Asterisks represent P<0.05 based on a 2-tailed Dunnett's test, relative to IFN-γ naïve controls.