TLR4, 5, and 9 Agonists Inhibit Murine Airway Invariant Natural Killer T Cells in an IL-12-Dependent Manner

Microbiome composition of airborne particulate matter from livestock farms and their effect on innate immune receptors and cells

Patients with respiratory diseases in rural areas have been reported to have enhanced responsiveness to ambient particulate matter (PM). In addition to the physical and chemical components, ambient PM can contain microorganisms or parts thereof, referred here as BioPM, that can also contribute to the adverse health effects. This study aimed to characterize the microbial composition of BioPM originating from livestock, and to investigate whether these BioPM can trigger the activation of innate receptors and cells. Coarse (PM_2.5-10 μm) and fine (PM_<2.5 μm) BioPM samples were collected from indoor chicken, pig and goat farms using the versatile aerosol concentration enrichment system (VACES) connected to a Biosampler. The fungal and bacterial communities were assessed with an amplicon based approach using Next Generation Sequencing (NGS). In parallel, HEK-Blue cells expressing different pattern recognition receptors (Toll like receptors (TLR) 2, 3, 4, 5, 7, 8, 9 and NOD 1, 2) and a human monocytic cell line (MM6) were exposed to BioPM samples from these sites. Distinct airborne microbiota profiles associated with the corresponding animal farm were observed. Moreover, the various BioPM contained mainly ligands for TLR2 and TLR4 resulting in a concentration-dependent increase of pro-inflammatory cytokine secreted by MM6 cells. In addition, we show for the first time that only the pig-derived BioPM induced TLR5 activation. These findings suggest that animal farm specific BioPM trigger distinct inflammatory responses, which may contribute to airway diseases in humans.

NKT cells contribute to basal IL-4 production but are not required to induce experimental asthma

CD1d-deficiency results in a selective deletion of NKT cells in mice that is reported to prevent murine allergic airway disease (AAD). Because we find 2–3 fold lower basal IL-4 production in CD1d^- mice than in wild-type (WT) mice, we hypothesized that the contribution made by NKT cells to AAD would depend on the strength of the stimulus used to induce the disease. Consequently, we compared CD1d-deficient mice to WT mice in the development of AAD, using several models of disease induction that differed in the type and dose of allergen, the site of sensitization and the duration of immunization. Surprisingly we found equivalent allergic inflammation and airway disease in WT and CD1d^- mice in all models investigated. Consistent with this, NKT cells constituted only ~2% of CD4⁺ T cells in the lungs of mice with AAD, and IL-4-transcribing NKT cells did not expand with disease induction. Concerned that the congenital absence of NKT cells might have caused a compensatory shift within the immune response, we administered an anti-CD1d monoclonal Ab (mAb) to block NKT function before airway treatments, before or after systemic sensitization to antigen. Such Ab treatment did not affect disease severity. We suggest that the differences reported in the literature regarding the significance of NKT cells in the induction of allergic airway disease may have less to do with the methods used to study the disease and more to do with the animals themselves and/or the facilities used to house them.

Nerve growth factor promotes expression of costimulatory molecules and release of cytokines in dendritic cells involved in Th2 response through LPS-induced p75NTR

INTRODUCTION

Nerve growth factor (NGF) plays an important role in asthmatic inflammatory responses. However, the effects of NGF on dendritic cells (DCs) in asthmatic inflammation remain unknown. Therefore, we examined the effects of NGF on co-stimulatory molecules and the release of cytokines after ovalbumin (OVA) and a low dose of LPS (low LPS) stimulation of dendritic cells.

METHODS

Bone-marrow-derived dendritic cells (BMDCs) were collected from 6- to 8-week-old wide or TLR4(-/-) mice. BMDCs were treated with OVA and/or low LPS for 12h, and then stimulated with NGF for 24h. ELISA and flow cytometry were performed to measure TSLP, IL-6, IL-10, and IL-12 production and MHCII and CD86 expression on BMDCs. BMDCs were exposed to p75 neurotrophin receptor (p75NTR) inhibitor (TAT-Pep5) or NF-kB inhibitor (QNZ) 30 min prior to NGF 1 h after NGF intervention, the levels of RelA and RelB in cytoplasmic and nuclear were detected by west blot. Co-cultured BMDCs with naïve CD4(+) T cells, and ELISA was used to detect IL-4 and INF-γ levels.

RESULTS

NGF was found to markedly promote OVA and low LPS-induced expression of MHCII, CD86, secretion of TSLP and IL-6, and Th2-response-stimulating capacity of BMDCs. NGF affected BMDCs through LPS-induced p75NTR expression. TAT-Pep5 or QNZ could attenuate the promotive effect of NGF.

CONCLUSIONS

NGF facilitates OVA with lowLPS-induced maturation of mouse BMDCs through LPS-up-regulated p75 NTR via activation of NF-κB pathways, providing another mechanism for the involvement of NGF in the Th2 response.

Flagellin Modulates the Function of Invariant NKT Cells From Patients With Asthma via Dendritic Cells

PURPOSE

Invariant natural killer T (iNKT) cells play a critical role in the pathogenesis of asthma. We previously reported the association between circulating Th2-like iNKT cells and lung function in asthma patients and the suppressive effect of Toll-like receptor 5 ligand flagellin B (FlaB) on asthmatic in a mouse model. Thus, we investigated whether FlaB modulates the function of circulating iNKT cells in asthmatic patients.

METHODS

Peripheral blood mononuclear cells (PBMCs) were treated with FlaB, and the secreted and intracellular cytokines of iNKT cells were evaluated by using ELISA and flow cytometry, respectively, following stimulation with α-galactosylceramide. Foxp3⁺ iNKT cells were also measured. To determine the effect of FlaB-treated dendritic cells (DCs) on iNKT cells, we co-cultured CD14⁺ monocyte-derived DCs and T cells from patients with house dust mite-sensitive asthma and analyzed intracellular cytokines in iNKT cells.

RESULTS

A reduction of IL-4 and IL-17 production by iNKT cells in PBMCs after FlaB treatment was alleviated following blocking of IL-10 signaling. A decrease in the frequencies of IL-4⁺ and IL-17⁺ iNKT cells by FlaB-treated DCs was reversed after blocking of IL-10 signaling. Simultaneously, an increase in Foxp3⁺ iNKT cells induced by FlaB treatment disappeared after blocking of IL-10.

CONCLUSIONS

FlaB may inhibit Th2- and Th17-like iNKT cells and induce Foxp3⁺ iNKT cells by DCs via an IL-10-dependent mechanism in asthmatic patients. In patients with a specific asthma phenotype associated with iNKT cells, FlaB may be an effective immunomodulator for iNKT cell-targeted immunotherapy.