The Role of Regulatory T cells in Childhood Asthma

• Main Authors: Yi-Giien Tsai, 蔡易晉
• Other Authors: Ching-Yuang Lin
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/80140856861363624669

博士 === 國立陽明大學 === 臨床醫學研究所 === 99 === Asthma is characterized by chronic airway inflammation with increased inflammatory cytokines. Loss of regulatory T (Treg) cells function appears to be a critical factor in the pathogenesis of human allergic asthma. Attention has focused on defects of naturally occurring CD4+CD25+ Tregs that regulate inflammatory response in asthmatic subjects. A synthetic Toll-like receptor (TLR) 2 ligand Pam3CSK4 could expand CD4+ Treg function was shown to have therapeutic potential with adjuvant during allergen-specific immunotherapy (IT). MyD88 is a major TLR adaptor to activate NF-κB, which acts as a master switch for allergic inflammation disease. In comparison with CD4+ Treg cells, the generation and function of CD8+ Treg cells during IT is less well defined. The aims of this study were to evaluate whether Dermatophagoides pteronyssinus IT could increase CD4+CD25+ Tregs with modulating MyD88 signaling proteins and expand CD8+CD25+Foxp3+ Treg population. The present study also investigated whether Pam3CSK4 could enhance CD8+ Treg suppressive function. Series of experiments were conducted in this study: Peripheral blood mononuclear cells (PBMCs) were isolated from patients before and after D. pteronyssinus IT and also from matched control subjects. Intracellular IL-10 and Foxp3 expression of CD4+CD25+ T cells and cell numbers and IL-10 and granzyme B production of CD8+CD25+Foxp3+ Treg cells were measured by flow-cytometry. The MyD88 signaling proteins of IL-1 receptor-associated kinase (IRAK)-1 in cytoplasm and IFN-regulator factor-3 (IRF-3) with NF-κB/p65 in sorted-purified CD4+ Tregs was determined by Western-blot analysis. In particular, we investigated the suppressive function of CD8+ Treg on CD4+ cells proliferation and CD4+CD45ROhi+ apoptosis after D. pteronyssinus 2 stimulation. The results showed patients undergoing IT produced more soluble CD14, IL-10, and TGF-β that correlated with FEV1 improvement. In the immunotherapy group, the number of CD4+Foxp3+ Treg cells and CD8+Foxp3+ Treg cells increased more than the baseline status. Increased IL-10 production with decreased IRAK-1 and NF-κB/p65 nuclear translocation was observed in sorted-purified CD4+ Treg cells. Costimulation of PBMCs with Pam3CSK4 and D. pteronyssinus 2 expanded the CD8+CD25+Foxp3+ Treg population and inhibited D. pteronyssinus 2-induced IL-4 production. Pam3CSK4-treated CD8+CD25+ Treg cells directly suppressed CD4+ T cell proliferation by cell-contact inhibition. TUNEL assay revealed that CD8+CD25+ Tregs, but not CD4+CD25+ Tregs, directly induced CD4+CD45ROhi+ cells apoptosis. Our results indicated that TH2 cells anergy and the relationship of immune tolerance during IT might be mediated by induction of CD4+ Treg cells and CD8+ Treg cells with anti-inflammatory cytokine. CD4+ CD25hi+ regulatory T cells may respond directly to Der p-2, and modulate MyD88 signaling proteins to inhibit nuclear NF-κB/p65 expression during IT. Our studies further provide direct evidence that Pam3CSK4 induces an immunomodulatory effect by inducing CD8+ Treg cells; therefore, it may be a good adjuvant for the treatment of mite allergies.