Increased frequency of circulating IL-21 producing Th-cells in patients with granulomatosis with polyangiitis (GPA)

Wayel H Abdulahad,Nikola Lepse,Henko Tadema,Pieter C Limburg,Minke G Huitema,Cees Gm Kallenberg,Abraham Rutgers,Coen A Stegeman,Berber Doornbos-Van Der Meer,Peter Heeringa

doi:10.1186/ar4247

Abstract

IntroductionThe present study aimed to explore a possible role for IL-21 producing Th-cells in the immunopathogenesis of granulomatosis with polyangiitis (GPA).MethodsPeripheral blood from 42 GPA patients in remission and 29 age-matched healthy controls (HCs) were stimulated in vitro, and the frequencies of IL-21 producing Th-cells were determined by flow cytometry. Since Th17-cells produce a low level of IL-21, IL-17 was also included in the analysis. Given that IL-21 is a hallmark cytokine for T follicular helper cells (TFH), we next evaluated the expression of their key transcription factor BCL-6 by RT-PCR and flow cytometry. To investigate the effect of IL-21 on autoantibody-production, PBMCs from GPA patients were stimulated in vitro with BAFF/IL-21 and total IgG and ANCA levels were measured in supernatants. In addition, the expression of IL-21-receptor on B-cells was analyzed.ResultsPercentages of IL-21 producing Th-cells were significantly elevated in GPA-patients compared to HCs, and were restricted to ANCA-positive patients. The expression of BCL-6 was significantly higher in ANCA-positive GPA-patients, as compared with ANCA-negative patients and HCs. IL-21 enhanced the production of IgG and ANCA in vitro in stimulated PBMCs from GPA patients. No difference was found in the expression of the IL-21-receptor on B-cells between ANCA-negative patients, ANCA-positive patients, and HCs.ConclusionThe increased frequency of circulating IL-21 producing Th-cells in ANCA-positive GPA patients and the stimulating capacity of IL-21 on ANCA-production suggest a role for these cells in the immunopathogenesis of GPA. Blockade of IL-21 could constitute a new therapeutic strategy for GPA.

Highlights

The present study aimed to explore a possible role for IL-21 producing Th-cells in the immunopathogenesis of granulomatosis with polyangiitis (GPA)
Increased percentage of circulating IL-21+IL-17- cells in anti-neutrophil cytoplasmic autoantibodies (ANCA)-positive GPA patients compared to ANCA-negative patients and healthy controls We initially determined the frequency of IL-21-producing CD4 T-cells in the peripheral blood of GPA patients (n = 42) and HCs (n = 29) after in vitro stimulation
Since Th17 cells are increased in GPA patients [10,11], we extended our analysis to investigate whether increased IL-21+ Th-cells in GPA patients resulted from an increase in Th17 cells

Summary

Introduction

The present study aimed to explore a possible role for IL-21 producing Th-cells in the immunopathogenesis of granulomatosis with polyangiitis (GPA). Granulomatosis with polyangiitis (GPA) is an autoimmune vasculitis of small- to medium-sized blood vessels, associated with the presence of circulating anti-neutrophil cytoplasmic autoantibodies (ANCA) that are mainly directed against proteinase 3 [1,2,3]. Multiple studies in animal models indicate a pivotal role of IL-21 in the pathogenesis of autoimmune diseases. Subsequent investigations demonstrated that blocking of the IL-21 pathway reduces levels of anti-dsDNA autoantibodies and prevents renal disease in mouse models of systemic lupus erythematosus (SLE) [15]. Recent genome-wide association studies have provided convincing evidence that genetic variants in the region on chromosome 4q27 that harbor the IL-21 and IL-2 genes are associated with chronic inflammatory disorders, including SLE, IBD and psoriasis [18,19,20]. IL-21 seems to play an important role in autoimmune diseases in general and could constitute a novel target for therapy

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