FIG. 9.

F. tularensis Schu S4 LPS and recombinant GroEL synergistically activate human macrophages. HuMDM were treated with 1 μg of Schu S4 GroEL/ml, 1 μg of Schu S4 LPS/ml, or a combination of the two stimuli (each at 1 μg/ml) for 24 h at 37°C in the presence of 20 μg of polymyxin B/ml. For controls, cells were incubated with either 10 ng of E. coli (Ec) LPS/ml or medium only (Unstim). Cell-free, conditioned media were collected and assayed for CXCL8 by ELISA. Bars indicate the means ± the SD of three replicate samples. *, Significantly greater than unstimulated samples (P < 0.001). The experiment was repeated two more times with similar results.