BMDMs were prepared from C57BL/6 (B6) or B6.C3H-sst1 congenic mice, as described in the Methods. Cells were infected with C. pneumoniae at an MOI of 3∶1, and supernatant harvested at 24 hpi for assay of the indicated cytokines. (A–D) In some cases, cells were pretreated with IFN-γ for 30 min at the indicated concentrations prior to infection. (E–F) For antibody neutralization, cells were pretreated with indicated neutralizing antibody (anti-IL-10 or anti-IFN-β) or isotype control at a concentration of 250 ng/ml prior to infection or IFN-γ treatment (10 U/ml). Data is shown as the mean ± SEM from triplicate wells. Significance: NS, No significant difference; *, p<0.05; **, p≤0.01; ***, p≤0.001; ****, p≤0.0001. The results are representative of at least 3 independent experiments.