TLR9 regulates the mycobacteria-elicited pulmonary granulomatous immune response in mice through DC-derived Notch ligand delta-like 4
Toshihiro Ito, … , Stephen W. Chensue, Steven L. Kunkel
Toshihiro Ito, … , Stephen W. Chensue, Steven L. Kunkel
Published December 15, 2008
Citation Information: J Clin Invest. 2009;119(1):33-46. https://doi.org/10.1172/JCI35647.
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Research Article Infectious disease

TLR9 regulates the mycobacteria-elicited pulmonary granulomatous immune response in mice through DC-derived Notch ligand delta-like 4

Abstract

TLR9 activation is important for the maintenance of mycobacteria-elicited pulmonary granulomatous responses, hallmarks of protective immune responses following mycobacterial infection. However, the mechanism or mechanisms underlying this effect of TLR9 are not clear. Here, we show that Tlr9-deficient mice challenged with a Mycobacterium antigen display an altered Th17 cytokine profile, decreased accumulation of granuloma-associated myeloid DCs, and profoundly impaired delta-like 4 (dll4) Notch ligand expression. Mechanistic analysis revealed that WT bone marrow–derived DCs but not macrophages promoted the differentiation of Th17 cells from bacillus Calmette-Guérin–challenged (BCG-challenged) lung CD4+ T cells. Both lung and bone marrow DCs isolated from Tlr9-deficient mice inoculated with Mycobacterium antigen expressed lower levels of dll4 Notch ligand than the same cells isolated from WT mice. Passively immunizing WT mice with neutralizing antibodies specific for dll4 during granuloma formation resulted in larger granulomas and lower levels of Th17-related cytokines. In addition, dll4 specifically regulated Th17 activation in vitro. Together, these results suggest dll4 plays an important role in promoting Th17 effector activity during a mycobacterial challenge. Furthermore, TLR9 seems to be required for optimal dll4 expression and the regulation of Mycobacterium antigen–elicited granuloma formation in mice.

Authors

Toshihiro Ito, Matthew Schaller, Cory M. Hogaboam, Theodore J. Standiford, Matyas Sandor, Nicholas W. Lukacs, Stephen W. Chensue, Steven L. Kunkel

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Figure 1

Tlr9–/– mice showed larger pulmonary granulomas and impaired Th17 cytokine levels.

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Tlr9–/– mice showed larger pulmonary granulomas and impaired Th17 cytok...
All panels compare parameters between WT and Tlr9–/– mice. (A) Lung tissues were histologically analyzed by H&E at day 4 after initiation of lung granuloma. Original magnification, ×100. (B) Kinetic analysis of the development of lung granulomas using morphometric analysis of the evolving lung lesions in WT and Tlr9–/– mice. Dotted line represents mean granuloma cross-sectional area (μm2) ± SEM. *P < 0.05; **P < 0.001. (C) Protein levels of IL-17 measured in whole lungs using a Luminex system. Data shown are mean ± SEM and are from a representative experiment of 4 independent experiments. †P < 0.01. (D–F) Quantitative real-time PCR (TaqMan) was performed to measure the transcript levels of IL-17A (D), IL-17F (E), IL-6, IL-21, IL-23p19, TGF-β, TNF-α, and IL-10 (F) in whole lungs. Data shown are mean ± SEM and are from a representative experiment of 4 independent experiments. Each time point indicates at least 4–6 mice per group.