Rheumatoid arthritis patients display B-cell dysregulation already in the na\xefve repertoire consistent with defects in B-cell tolerance

Yan Wang,Vivianne Malmström,Anna Svärd,Radha Thyagarajan,Katy A Lloyd,Ioannis Melas,Karin Lundberg,Monika Hansson,Lars Klareskog,Stephen Rapecki,Alf Kastbom,Joakim Lindqvist,Linda Mathsson-Alm,Anca I Catrina,Diana Zhou,Caroline Grönwall

doi:10.1038/s41598-019-56279-0

Abstract

B cells are postulated to be central in seropositive rheumatoid arthritis (RA). Here, we use exploratory mass cytometry (n = 23) and next-generation sequencing (n = 19) to study B-cell repertoire shifts in RA patients. Expression of several B-cell markers were significantly different in ACPA+ RA compared to healthy controls, including an increase in HLA-DR across subsets, CD22 in clusters of IgM+ B cells and CD11c in IgA+ memory. Moreover, both IgA+ and IgG+ double negative (IgD− CD27−) CD11c+ B cells were increased in ACPA+ RA, and there was a trend for elevation in a CXCR5/CCR6high transitional B-cell cluster. In the RA BCR repertoire, there were significant differences in subclass distribution and, notably, the frequency of VH with low somatic hypermutation (SHM) was strikingly higher, especially in IgG1 (p < 0.0001). Furthermore, both ACPA+ and ACPA− RA patients had significantly higher total serum IgA and IgM compared to controls, based on serology of larger cohorts (n = 3494 IgA; n = 397 IgM). The observed elevated Ig-levels, distortion in IgM+ B cells, increase in double negative B cells, change in B-cell markers, and elevation of unmutated IgG+ B cells suggests defects in B-cell tolerance in RA. This may represent an underlying cause of increased polyreactivity and autoimmunity in RA.

Highlights

B cells are postulated to be central in seropositive rheumatoid arthritis (RA)
The most prominent differentially expressed marker was HLA-DR, which was increased in anti-citrullinated protein autoantibodies (ACPA)+ RA compared to controls across B-cell clusters, including clusters that represent both naïve and memory B-cell populations, irrespectively of the Ig isotype (Fig. 1B, fold change = 1.6–2.1)
While circulating IgA cells were lower in both mass cytometry and B-cell receptor (BCR) sequence analysis, when we analyzed total IgA levels in 2194 RA patients 1300 population controls (Fig. 4, Supplemental Table 10), we found that IgA levels were significantly elevated in RA compared to controls (2.32 ± 1.0 [median 2.21] vs 1.58 ± 0.80 mg/ml [median 1.51], p < 0.0001)

Summary

Introduction

B cells are postulated to be central in seropositive rheumatoid arthritis (RA). Here, we use exploratory mass cytometry (n = 23) and next-generation sequencing (n = 19) to study B-cell repertoire shifts in RA patients. Natural IgM are produced by specialized innate-like B cells, spontaneously expressed from birth in a T-cell independent manner, and are germline encoded (reviewed in[26,27]) While these IgM have anti-inflammatory properties and have been hypothesized to be beneficial due to their role in clearance of dead cells and modified biomolecules[28,29,30], the B cells may act as a pool of polyreactive and self-reactive cells that could get engaged during break-of tolerance and lead to T-cell dependent pathogenic autoreactivity. By using an in-depth B-cell focused methodology, we can start to decipher the underlying B-cell repertoire changes in RA in detail

Methods

Results

Conclusion