Role of IL-35 in sublingual allergen immunotherapy.

BACKGROUND: Grass pollen-specific immunotherapy involves immunomodulation of allergen-specific TH2 responses and induction of IL-10+ and/or TGF-ß+CD4+CD25+ regulatory T cells (induced Treg cells). IL-35+CD4+CD25+ forkhead box protein 3-negative T (IL-35-inducible regulatory T [iTR35]) cells have been reported as a novel subset of induced Treg cells with modulatory characteristics. OBJECTIVE: We sought to investigate mechanisms underlying the induction and maintenance of immunologic tolerance induced by IL-35 and iTR35 cells. METHODS: The biological effects of IL-35 were assessed on group 2 innate lymphoid cells (ILC2s); dendritic cells primed with thymic stromal lymphopoietin, IL-25, and IL-33; and B and TH2 cells by using flow cytometry and quantitative RT-PCR. Grass pollen-driven TH2 cell proliferation and cytokine production were measured by using tritiated thymidine and Luminex MagPix, respectively. iTR35 cells were quantified in patients with grass pollen allergy (seasonal allergic rhinitis [SAR] group, n = 16), sublingual immunotherapy (SLIT)-treated patients (SLIT group, n = 16), and nonatopic control subjects (NACs; NAC group, n = 16). RESULTS: The SAR group had increased proportions of ILC2s (P = .002) and IL-5+ cells (P = .042), IL-13+ cells (P = .042), and IL-5+IL-13+ ILC2s (P = .003) compared with NACs. IL-35 inhibited IL-5 and IL-13 production by ILC2s in the presence of IL-25 or IL-33 (P = .031) and allergen-driven TH2 cytokines by effector T cells. IL-35 inhibited CD40 ligand-, IL-4-, and IL-21-mediated IgE production by B cells (P = .015), allergen-driven T-cell proliferation (P = .001), and TH2 cytokine production mediated by primed dendritic cells. iTR35 cells suppressed TH2 cell proliferation and cytokine production. In addition, allergen-driven IL-35 levels and iTR35 cell counts were increased in patients receiving SLIT (all, P < .001) and NACs (all, P < .001) compared with patients with SAR. CONCLUSION: IL-35 and iTR35 cells are potential novel immune regulators induced by SLIT. The clinical relevance of SLIT can be underscored by restoration of protective iTR35 cells.