FIG. 7.

F. tularensis LVS GroEL stimulates human macrophages through a TLR4-dependent mechanism. (A) HuMDM were preincubated for 1 h at 37°C with either 10 μg of a MAb to TLR2/ml, 10 μg of a MAb to TLR4/ml, or a combination of both. Similarly, an isotype-matched control IgG2a MAb was used at 20 μg/ml. The cells were then stimulated with 2 μg of LVS GroEL/ml in the presence of antibody and 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). (B) HuMDM were incubated in medium only (Unstim) or with a combination of 1 μg of LVS GroEL/ml and 1 μg of LVS LPS/ml in the absence of antibody or in the presence of 10 μg of a MAb to TLR4/ml or an isotype-matched control IgG2a MAb. Cell-free, conditioned media were collected and assayed for CXCL8 by ELISA. Bars indicate the means ± the SD of three replicate samples. *, Significantly less than GroEL in the absence of a MAb (P < 0.001). The experiment in panel A was repeated three more times with similar results.