Toll-like receptor 2-expressing macrophages are required and sufficient for rhinovirus-induced airway inflammation.
J Allergy Clin Immunol 2016;
138:1619-1630. [PMID:
27084403 DOI:
10.1016/j.jaci.2016.01.037]
[Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 12/29/2015] [Accepted: 01/22/2016] [Indexed: 12/26/2022]
Abstract
BACKGROUND
We have shown that rhinovirus, a cause of asthma exacerbation, colocalizes with CD68+ and CD11b+ airway macrophages after experimental infection in human subjects. We have also shown that rhinovirus-induced cytokine expression is abolished in Toll-like receptor (TLR2)-/- bone marrow-derived macrophages.
OBJECTIVE
We hypothesize that TLR2+ macrophages are required and sufficient for rhinovirus-induced airway inflammation in vivo.
METHODS
Naive and ovalbumin (OVA)-sensitized and challenged C57BL/6 wild-type and TLR2-/- mice were infected with RV1B, followed by IgG or anti-TLR2, to determine the requirement and sufficiency of TLR2 for rhinovirus-induced airway responses. Bone marrow chimera experiments using OVA-treated C57BL/6 and TLR2-/- mice were also performed. Finally, naive TLR2-/- mice underwent intranasal transfer of bone marrow-derived wild-type macrophages.
RESULTS
RV1B infection of naive wild-type mice induced an influx of airway neutrophils and CD11b+ exudative macrophages, which was reduced in TLR2-/- mice. After allergen exposure, rhinovirus-induced neutrophilic and eosinophilic airway inflammation and hyperresponsiveness were reduced in TLR2-/- and anti-TLR2-treated mice. Transfer of TLR2-/- bone marrow into wild-type, OVA-treated C57BL/6 mice blocked rhinovirus-induced airway responses, whereas transfer of wild-type marrow to TLR2-/- mice restored them. Finally, transfer of wild-type macrophages to naive TLR2-/- mice was sufficient for neutrophilic inflammation after rhinovirus infection, whereas macrophages treated with IL-4 (to induce M2 polarization) were sufficient for eosinophilic inflammation, mucous metaplasia, and airways hyperresponsiveness.
CONCLUSIONS
TLR2 is required for early inflammatory responses induced by rhinovirus, and TLR2+ macrophages are sufficient to confer airway inflammation to TLR2-/- mice, with the pattern of inflammation depending on the macrophage activation state.
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