IL-35+ Regulatory T Cells Suppress Grass Pollen-Driven Th2 Responses and Are Induced Following Grass Pollen-Specific Sublingual Immunotherapy

Abstract

Inducible IL-35 producing T cells are a novel subset of regulatory T cells (iTR35). We hypothesized that i) iTR35 suppress grass pollen-specific Th2 responses following ex-vivo allergen stimulation in an IL-35-dependent manner ii) iTR35 are induced following grass pollen-specific sublingual immunotherapy T effector cells from grass pollen allergics (n=9) were co-cultured with irradiated APCs and 3mcg/mL of Phleum pratenseextract in the presence/absence of iTR35 cells. Th2 cytokines and proliferative responses were measured by Luminex MagPix assay and 3H-thymidine incorporation, respectively. We quantified iTR35 cells, IL-10 and Foxp3+ Tregs in PBMCs obtained from grass pollen sublingual immunotherapy (SLIT)-treated patients, untreated allergic subjects and non-atopic controls. iTR35 cells significantly suppressed Th2 cytokines (IL-4, p=0.002; IL-5, p=0.001 and IL-13, p<0.001) and grass pollen-driven proliferative responses (p=0.006). This suppression was IL-35 (p=0.004), partially IL-10 (p=0.02) but not TGF-b-dependent. In untreated allergics, iTR35 cells (p=0.03) and IL-10+Tregs (p=0.03) were lower compared to non-atopic controls. Interestingly, the SLIT-treated group had higher proportions of iTR35 cells and IL-10+ Tregs compared to untreated allergic controls. In the SLIT-treated group, mRNA expression for IL-12p35 (p=0.01), EBI3 (p=0.04) and IL-10 (p=0.02) in allergen stimulated PBMCs was increased compared to untreated allergic controls. Foxp3+ Tregs were lower in untreated allergics (p=0.03) and the SLIT-treated group (p=0.03) compared to non-allergic controls, whereas ‘activated’ GARP+Foxp3+ T regs were increased in the SLIT-treated group (p=0.03) compared to controls. iTR35 cells suppress grass pollen-driven memory Th2 cell responses and are induced following SLIT. Whether iTR35 cells contribute to long-term tolerance remains to be tested.