Role of IL-35 in sublingual allergen immunotherapy

Background Grass pollen–specific immunotherapy involves immunomodulation of allergen-specific T H 2 responses and induction of IL-10 + and/or TGF-β + CD4 + CD25 + regulatory T cells (induced Treg cells). IL-35 + CD4 + CD25 + forkhead box protein 3–negative T (IL-35–inducible regulatory T [iT R 35]) 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 iT R 35 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 T H 2 cells by using flow cytometry and quantitative RT-PCR. Grass pollen–driven T H 2 cell proliferation and cytokine production were measured by using tritiated thymidine and Luminex MagPix, respectively. iT R 35 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 T H 2 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 T H 2 cytokine production mediated by primed dendritic cells. iT R 35 cells suppressed T H 2 cell proliferation and cytokine production. In addition, allergen-driven IL-35 levels and iT R 35 cell counts were increased in patients receiving SLIT (all, P P Conclusion IL-35 and iT R 35 cells are potential novel immune regulators induced by SLIT. The clinical relevance of SLIT can be underscored by restoration of protective iT R 35 cells.