Altered chromatin landscape in circulating T follicular helper and regulatory cells following grass pollen subcutaneous and sublingual immunotherapy

Background: Allergen-specific immunotherapy is a disease-modifying treatment that induces long-term T-cell tolerance. Objective: We sought to evaluate the role of circulating CXCR5(+)PD-1(+) T follicular helper (cT(FH)) and T follicular regulatory (T-FR) cells following grass pollen subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) and the accompanying changes in their chromatin landscape. Methods: Phenotype and function of cT(FH) cells were initially evaluated in the grass pollen-allergic (GPA) group (n = 28) and nonatopic healthy controls (NAC, n = 13) by mathematical algorithms developed to manage high-dimensional data and cell culture, respectively. cT(FH) and T-FR cells were further enumerated in NAC (n = 12), GPA (n = 14), SCIT- (n = 10), and SLIT- (n = 8) treated groups. Chromatin accessibility in cT(FH) and T-FR cells was assessed by assay for trans-posaseaccessible chromatin sequencing (ATAC-seq) to investigate epigenetic mechanisms underlying the differences between NAC, GPA, SCIT, and SLIT groups. Results: cT(FH) cells were shown to be distinct from T(H)2- and T(H)2A-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 cT(FH)-cell proliferation in the GPA group but not in the NAC group (P<.05). cT(FH) cells were higher in the GPA group compared with the NAC group and were lower in the SCIT and SLIT groups (P<.01). Time-dependent induction of IL-4, IL-21, and IL-6 was observed in nasal mucosa following intranasal allergen challenge in the GPA group but not in SCIT and SLIT groups. TFR and IL-101 cT(FH) cells were induced in SCIT and SLIT groups (all, P<.01). ATAC-seq analyses revealed differentially accessible chromatin regions in all groups. Conclusions: For the first time, we showed dysregulation of cT(FH) cells in the GPA group compared to NAC, SCIT, and SLIT groups and induction of T-FR and IL-101 cT(FH) cells following SCIT and SLIT. Changes in the chromatin landscape were observed following allergen-specific immunotherapy in cT(FH) and T-FR cells.

Automated summary

This study aimed to evaluate the role of circulating CXCR5(+)PD-1(+) T follicular helper (cT(FH)) and T follicular regulatory (T-FR) cells in grass pollen allergic patients following different immunotherapy treatments. The findings showed dysregulation of cT(FH) cells in the grass pollen allergic group compared to nonatopic healthy controls, as well as induction of T-FR and IL-101 cT(FH) cells following specific immunotherapy. Changes in chromatin landscape were observed in cT(FH) and T-FR cells post-immunotherapy.