Response of C57Bl/6 and FcR k/o murine DC to Ab-opsonized C. burnetii. Bone marrow-derived dendritic cells were generated from B6 or FcR k/o mice. The cells were mock infected, or infected for 24 h with C. burnetii (Cb), C. burnetii that had been incubated with naïve mouse serum (Cb +naive) or C. burnetii that had been incubated with mouse immune serum (Cb +immune). Treatment of DC with E. coli LPS served as a positive control for stimulation. The concentrations of TNF and IL-6 in the DC supernatants were determined by BioPlex multiplex cytokine assay. Levels below the limits of detection of the assay are indicated with an asterisk. The results shown are from one experiment and are representative of three independent experiments.