Published ahead of print on January 17, 2008, doi:10.1164/rccm.200709-1387OC Am. J. Respir. Crit. Care Med., Volume 177, Number 7, April 2008, 720-729 A more recent version of this article appeared on April 1, 2008
Submitted on September 18, 2007 Toll-like Receptor 2 Down-regulation in Mouse Allergic Lungs Decreases Mycoplasma ClearanceQun Wu1,1 Department of Medicine, National Jewish Medical and Research Center and the University of Colorado Health Sciences Center, Denver, CO, USA * To whom correspondence should be addressed. E-mail: chuhw{at}njc.org.
Rationale: Respiratory Mycoplasma pneumoniae (Mp) infection is involved in asthma pathobiology, but whether the established airway allergic inflammation compromises lung innate immunity and subsequently predisposes asthmatics to Mp infection remains unknown.
Objectives: To test whether the established airway allergic inflammation compromises host innate immunity [e.g., Toll-like receptor 2 (TLR2)] to hinder the elimination of Mp from the lungs.
Methods: We used mouse models of ovalbumin (OVA)-induced airway allergic inflammation with an ensuing Mp infection, and cultures of mouse primary lung dendritic cells (DCs) and bone marrow-derived DCs (BMDCs).
Measurements and Main Results: Lung Mp clearance in allergic mice, TLR2 and IL-6 levels in lung cells including DCs as well as in cultured primary lung DCs and BMDCs were assessed. The established OVA-induced airway allergic inflammation, or the prominent Th2 cytokines IL-
4 and IL-13, inhibited TLR2 expression and IL-6 production in lung cells including lung DCs, and eventually led to impaired host defense against Mp. Studies in IL-6 knockout mice indicated that IL-6 directly promoted Mp clearance from the lungs. IL-4 and IL-13-induced suppression of
TLR2 was mediated by inhibiting nuclear factor- Key words: asthma; lung; innate immunity; bacterial clearance
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