IFN-γ up-regulates Th17/IL-17 response against Chlamydia trachomatis lung infection

Objective: To investigate the regulation of IFN-γ to Th17 response in Chlamydia muridarum (Cm) lung infection in mice. Methods: A murine model of pneumonia induced by intranasal inoculation of Cm was used for this study. Anti-mouse IFN-γ McAbs were used to neutralize endogenous IFN-γ following Cm lung infection. Control group received the same dose of isotype antibody (IgG2a), Mice were sacrificed at day 7 postinfection. Chlamydial growth in the lung was assessed by immunoenzyme technique. IL-17 and IL-23 mRNA expression in the lung was assayed by RT-PCR and the proliferation of IL-17 + CD4 + T cells in the spleen was assayed by intracellular cytokine staining. Results: IFN-γ-neutralized mice exhibited serious disease course, include greater body weight loss, higher organism growth and much more severe pathological changes in the lung compared with control mice. The mRNA expression of IL-17 and IL-23 in the lung and the proliferation of IL-17 + CD4 + T cells in the spleen significantly decreased in the IL-17-neutralized mice. Conclusion: IFN-γ was protective in Cm lung infection through up-regulating the antigen specific Th17 responses.