title: Type I IFNs enhance susceptibility to Chlamydia muridarum lung infection by enhancing apoptosis of local macrophages.
abstract: Type I IFNs (IFNIs) have pleiotropic functions in regulating host innate and adaptive immune responses to pathogens. To elucidate the role of IFNIs in host resistance to chlamydial infection in vivo, we compared IFN-alpha/beta receptor knockout (IFNAR(-/-)) and wild-type control mice in susceptibility to Chlamydia trachomatis mouse pneumonitis (Chlamydia muridarum) lung infection. We found that the IFNAR(-/-) mice were significantly more resistant to C. muridarum infection showing less bacterial burden and bodyweight loss, and milder pathological changes. However, IFN-gamma response, which is believed to be critical in host defense against chlamydial infection, was similar between the wild-type and IFNAR(-/-) mice. More importantly, TUNEL analysis showed less macrophage apoptosis in IFNAR(-/-) mice, which was consistent with lower expressions of IFNI-induced apoptotic factors, TRAIL, Daxx, and PKR. Furthermore, depletion of lung macrophages with dichloromethylene diphosphonate-liposome significantly increased the susceptibility of the IFNAR(-/-) mice to C. muridarum, confirming the importance of macrophages. Overall, the data indicate that IFNIs play a promoting role in C. muridarum lung infection, largely through increase of local macrophage apoptosis.
authors.affiliation: Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Qiu
authors.forename: Yijun
authors.initials: Y
authors.lastname: Fan
authors.forename: Antony George
authors.initials: AG
authors.lastname: Joyee
authors.forename: Shuhe
authors.initials: S
authors.lastname: Wang
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Han
authors.forename: Hong
authors.initials: H
authors.lastname: Bai
authors.forename: Lei
authors.initials: L
authors.lastname: Jiao
authors.forename: Nico
authors.initials: N
authors.lastname: Van Rooijen
authors.forename: Xi
authors.initials: X
authors.lastname: Yang
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D017209:Apoptosis / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D002465:Cell Movement / Q000276:immunology; D018925:Chemokines / Q000096:biosynthesis; D002690:Chlamydia Infections / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D023502:Chlamydia muridarum / Q000276:immunology*; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology; D004198:Disease Susceptibility; D005260:Female; D007370:Interferon Type I / Q000276:immunology*; D008171:Lung Diseases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008264:Macrophages / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D053633:Receptor, Interferon alpha-beta / Q000172:deficiency / Q000235:genetics / Q000378:metabolism
chemical_list: D000906:Antibodies; D018925:Chemokines; D007370:Interferon Type I; D053633:Receptor, Interferon alpha-beta