Soluble MD-2 enhances TLR4-expressing cell response to whole Gram-negative, but not Gram-positive bacteria. TLR4-HEK293 cells were cultured with 3.2 multiplicity of infection (MOI) heat inactivated bacteria (E coli K12, E coli wild type, S aureus, and E coli K12 LPS as a positive control) in the presence (filled bars) or absence (empty bars) of 1 μg/mL polyHis-tagged recombinant human soluble MD-2 or an irrelevant poly-His-tagged protein (murine IL-6). IL-8 secretion in conditioned supernatants was measured by ELISA. Mean values plus or minus SD are shown. This is one representative experiment of 3 experiments.