TLR ligands of ryegrass pollen microbial contaminants enhance Th1 and Th2 responses and decrease induction of Foxp3hi regulatory T cells

Authors

  • Diana Mittag,

    Corresponding author
    1. Department of Allergy, Immunology and Respiratory Medicine, Alfred Hospital and Monash University, Melbourne, Australia
    2. Transfusion Research, Australian Red Cross Blood Services, Melbourne, Australia
    • Department of Immunology, Monash University, Melbourne, Australia
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  • Nirupama Varese,

    1. Department of Immunology, Monash University, Melbourne, Australia
    2. Department of Allergy, Immunology and Respiratory Medicine, Alfred Hospital and Monash University, Melbourne, Australia
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  • Anja Scholzen,

    1. Department of Immunology, Monash University, Melbourne, Australia
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  • Ashley Mansell,

    1. Monash Institute of Medical Research, Monash University, Melbourne, Australia
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  • Gillian Barker,

    1. Translational Proteomics, Baker Heart Institute, Melbourne, Australia
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  • Gregory Rice,

    1. Translational Proteomics, Baker Heart Institute, Melbourne, Australia
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  • Jennifer M. Rolland,

    1. Department of Immunology, Monash University, Melbourne, Australia
    2. Department of Allergy, Immunology and Respiratory Medicine, Alfred Hospital and Monash University, Melbourne, Australia
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  • Robyn E. O'Hehir

    1. Department of Immunology, Monash University, Melbourne, Australia
    2. Department of Allergy, Immunology and Respiratory Medicine, Alfred Hospital and Monash University, Melbourne, Australia
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Full correspondence: Dr. Diana Mittag, Transfusion Research, Australian Red Cross Blood Services, 100-154 Batman St, West Melbourne 3003, Australia

Fax: +61-3-96940-0244

e-mail: dianamittag@gmail.com

Abstract

Microbial contamination of grass pollens could affect sensitization, subsequent allergic response, and efficacy of allergen-specific immunotherapy. We investigated whether bacterial immunomodulatory substances can direct PBMC responses of allergic and nonatopic subjects against ryegrass pollen (RGP) toward Th1, Th2, or regulatory T (Treg) cells. Aqueous extracts of RGP with high or low LPS were fractionated into large and small molecular weight (MW) components by diafiltration. CFSE-labeled PBMCs from allergic and nonatopic subjects were stimulated with RGP extracts (RGPEs) and analyzed for cytokine secretion and T-cell responses. High LPS RGPE increased IFN-γ+ Th1 and IL-4+ Th2 effector cell induction and consistently decreased CD4+Foxp3hi Treg-cell induction. IL-10-producing T-cell frequency was unaltered, but IL-10 secretion was increased by high LPS RGPE. RGPE-stimulation of TLR-transfected cell lines revealed that high LPS pollen also contained a TLR2-ligand, and both batches a TLR9-ligand. Beta-1,3-glucans were detected in large and small MW fractions and were also T-cell stimulatory. In conclusion, coexposure to allergen and proinflammatory microbial stimuli does not convert an established Th2- into a Th1-response. Instead, proinflammatory responses are exacerbated and Foxp3hi Treg-cell induction is decreased. These findings show that adjuvants for specific immunotherapy should enhance Treg cells rather than target immune deviation from Th2 to Th1.

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