Figure 6

Dose–response curves of NF-κB induction by whole bacterial cells and LPS of E. coli BL21 (DE3) strains. The samples were assayed with HEK-Blue hTLR4 (A and C) and Null2 (B and D) cells for relative NF-κB induction by colorimetric determination of NF-κB-dependent SEAP activity. Relative NF-κB induction was measured following stimulation of HEK-Blue hTLR4 and Null2 cells with tenfold serial dilutions of whole bacterial cells (A and B) and LPS extracts (C and D) of E. coli BL21 (DE3) and BL21 (DE3)-derived KPM mutants, respectively. The values represent the means and standard deviations from three individual experiments. In all experiments, assayed samples displayed negligible activation of parental HEK-Blue Null2 cells, suggesting specific induction of NF-κB-dependent SEAP expression via the hTLR4/MD-2 signaling pathway in HEK-Blue hTLR4 cells.