Background B cells may form ectopic lymphoid-like structures in the synovium of patients with psoriatic arthritis (PsA) but the significance of this finding is not clear. A recent study found high frequency of autoantibodies in PsA1. Whether regulatory B cells (Bregs) are decreased or not in PsA is not clear.
Objectives To assess the phenotypic and functional characteristics of Breg subsets, CD19(pos)CD27(pos)CD24(high) memory and CD19(pos)CD24(high)CD38(high) transitional Bregs in patients with PsA.
Methods Peripheral blood mononuclear cells, isolated from 61 PsA patients, 21 patients with psoriasis (Ps) and 15 normal controls (NCs), were assessed. The expression of surface CD19, CD24, CD27 and CD38 and cytoplasmic IL-10 by Bregs was examined by flow cytometry following 24 hour bacterial CpG (ODN2006) stimulation using fluorochrome-conjugated monoclonal antibodies. We also measured IL-17 expression from T cells (Th17 cells) stimulated with PMA plus Ionomycin for 5 hours followed by intracellular staining (BD Biosciences).
Results Transitional Bregs were significantly decreased in PsA patients compared to NCs (0.72±0.54 vs1.56±0.58, p=0.000) and in Ps compared to NCs (1.08±0.38 vs 1.56±0.58, p=0.016, as well as in PsA compared to Ps patients (p=0.002). Memory Bregs were significantly decreased in PsA patients compared to NCs (2.93±2.31vs 6.94±2.03, p=0.000) and in Ps patients (2.97±1.83) compared to NCs (p=0.000) but did not differ between PsA and Ps patients. The impairment of Bregs in PsA was not associated with number of swollen or tender joints, CRP, ESR, or treatment with biologics. IL-10-producing Bregs inversely correlated with Th17 cells in PsA and in Ps.
Conclusions PsA exhibits numerical decrease and functional impairment of Bregs, especially of transitional Bregs. IL-10-producing Bregs inversely correlate with Th17 cells. The impairment of IL-10-producing Bregs may contribute to the pathogenesis of psoriatic disease.
Dolcino M et al. PLoSone 2014;9:e115424
Acknowledgement Financial support by ELKE, University of Thessaly
Disclosure of Interest None declared