Background IL-10-producing regulatory B cells (Bregs), also known as B10 cells, are decreased and functionally impaired in patients with systemic sclerosis (SSc), particularly in those with SSc-associated interstitial lung disease (1). As serum 25-OH-vitamin D (vitD) levels are associated with clinical aspects in patients with SSc (2), we investigated whether there is any link between vitD levels and Breg levels.

Objectives To assess whether or not vitD deficiency in SSc is associated with the percentages of circulating IL-10-producing Breg cells.

Methods PBMCs and serum samples were isolated from 55 patients with systemic sclerosis. Serum VitD levels were measured using a commercially available sandwich ELISA kit. Phenotypic analysis of CD19, CD24, CD27, CD38 and intracellular expression of cytoplasmic IL-10 following bacterial CpG (ODN2006) and PMA/ionomycin stimulation was examined by flow cytometry using specific fluorochrome-conjugated monoclonal antibodies (BD Biosciences).

Results Systemic sclerosis patients were divided into two groups (vitD deficient or not) based on a serum concentration cut off value of 20 ng/ml. The mean vitD levels in the deficient group were 14.11±3.6 ng/ml (n=17) whereas the mean vitD levels in the non-deficient group were 37.5±12.9 ng/ml (n=38). IL-10-producing B cells (B10 cells) were significantly decreased in vitD deficient patients compared to those with medium/high levels (p=0.02). CD19+CD27+ (memory) B cells were also significantly reduced in patients with VitD deficiency (p=0.004). In addition the ratio of naïve/memory B cells was significantly higher in VitD deficient patients (p<0.05). Within the memory B cell fraction, the CD19+CD27+CD24hi cells also known as phenotypic memory Bregs, were mostly decreased (p=0.001). There was no significant association between CD19+CD38hiCD24hi (transitional) Bregs and VitD levels.

Conclusions Our data suggest that vitamin D deficiency may account for reduced B10 cells in systemic sclerosis

References

1. Mavropoulos et al Arthritis Rheumatol. 2016;68:494–504.

2. Arnson Y et al Autoimmun Rev. 2011;10:490–4.

References

Disclosure of Interest None declared