Background IgG4-related disease (IgG4-RD) is a novel disease entity characterised by elevated serum IgG4 levels, IgG4(+) plasmacytic infiltration and fibrosis in various organs. We hypothesised that, if elevated IgG4 titers would be caused by antigen-driven immune responses, clonally expanded, IgG4(+) B cells and plasma cells might be present in affected tissue and peripheral blood.
Objectives To analyse the presence of IgG4(+) expanded B-cell clones in peripheral blood (PB) before and after successful therapy of patients with IgG4-associated cholangitis (IAC), and to compare this to healthy and disease controls using a newly developed high throughput sequencing (HTS) protocol for analysis of the B-cell receptor (BCR) repertoire.
Methods In 6 IAC patients the BCR repertoire was assessed in PB before and after 4 and 8 weeks of prednisolone (median 40mg, range 20–40 mg) treatment. As controls 6 healthy controls (HC) and 6 treatment-naive disease controls with PSC and pancreaticobiliary cancer were analysed (DC). In two patients a paired duodenal papilla biopsy was obtained at baseline. After isolation of mRNA the BCRheavy-chain was amplified, including the CDR3 region, thus fingerprinting unique clones. In our HTS protocol the number of clonal reads can be used as a measure for ‘dominance’; clones with a frequency of >0.5% were considered dominant.
Results At baseline, a mean of 15.1% of all clones was IgG(+) in IAC (similar in HC/DC). Among the IAC IgG(+) clones, the most dominant ones were IgG4(+) (mean rank: 1st in IAC versus 63th in HC (p < 0.005) and 55th in DC (p < 0.005)). Across all isotypes in every IAC patient IgG4(+) BCR clones were present among the 10 most dominant BCR clones which was not observed in any of the controls. The papilla contained the same dominant IgG4(+) clones that were detected in the paired blood samples. After 4 and 8 weeks of therapy, the contribution of IgG4(+) clones specifically to the BCR-repertoire was negligible (median 0.19%, IQR 0.16–0.21%), mirroring a sharp decline in serum IgG4 in conjunction with regression of clinical symptoms.
Conclusions Our findings indicate that IgG4(+) clones are abundantly present within the repertoire of IAC patients, in contrast to healthy or disease controls. The inflamed tissue was shown to contain the same expanded IgG4(+) clones, suggesting an antigen-driven immune response in IgG4-RD. A possible central role for IgG4(+) B cells is furthermore supported by the finding that IgG4(+) clones in peripheral blood specifically disappear upon successful corticosteroid therapy.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.