Figure 6. Neutralization of IFN-β protects cells from death and enhances C. pneumoniae replication.

BMDMs prepared from C57BL/6 (B6) or B6.C3H-sst1 mice were infected with C. pneumoniae (MOI 3∶1) in the presence or absence of IFN-γ (5 U/ml). The ratio of dead cells to total cell number was calculated using propidium iodide and Hoechst staining, as described in the Methods section, and is reported as the percent cytotoxicity. Where indicated, antibody neutralization was carried out using neutralizing antibody against IL-10 or IFN-β, or isotype control at a concentration of 250 ng/ml prior to infection or IFN-γ treatment. A: Cytotoxicity was determined over time at 24, 48 and 72 hpi in Cp infected BMDM, and is reported as percent cell death. B: Effect of IL-10 and IFN-β neutralization on Cp-induced cytotoxicity at 72 hpi. C: Effect of IL-10 and IFN-β neutralization on Cp growth. Infected BMDM were lysed at 69 hpi, and recovered EBs were quantitatively cultured, as described in the Methods. All data shown above represents the mean ± SEM from triplicate wells, and is representative of at least two independent experiments. Significance: *, p<0.05; **, p≤0.01; ***, p≤0.001.