Grass pollen immunotherapy alters chromatin landscape in circulating T follicular and regulatory cells.

Abstract: Background Allergen-specific immunotherapy (AIT) is a disease-modifying treatment that induces long-term T cell tolerance. Objective To evaluate the role of circulating CXCR5+PD-1+T follicular helper (cTFH) and T follicular regulatory (TFR) cells following grass pollen subcutaneous (SCIT) and sublingual (SLIT) immunotherapy and the accompanying changes in their chromatin landscape. Methods Phenotype and function of cTFH cells were initially evaluated in grass pollen-allergics (GPA, n= 28) and non-atopic controls (NAC, n=13) by mathematical algorithms developed to manage high-dimensional data and cell culture, respectively. cTFH and TFR cells were further enumerated in NAC (n=12), GPA (n=14), SCIT (n=10) and SLIT (n=8)-treated groups. Chromatin accessibility in cTFH and TFR cells was assessed by ATAC-seq to investigate epigenetic mechanisms underlying the differences between NAC, GPA, SCIT and SLIT. Results: cTFH cells were shown to be distinct from TH2 and TH2A cell subsets, capable of secreting IL-4 and IL-21. Both cytokines synergistically promoted B cell class switching to IgE and plasma cell differentiation. Grass pollen allergen induced cTFH cell proliferation in GPA but not in NAC (P Conclusion For the first time, we showed dysregulation of cTFH cells in GPA compared to NAC, SCIT and SLIT and induction of TFR and IL-10+ cTFH cells following SCIT and SLIT. Changes in the chromatin landscape were observed following AIT in cTFH and TFR cells.