Objectives: Systemic sclerosis (SSc) is an autoimmune disease with fibrosis, microangiopathy and immune dysfunction. B cell abnormalities characterised by autoantibody production and polyclonal B cell activation play an important role in the pathogenesis of SSc. We previously identified an expansion of functional and activated circulating T follicular helper (cTfh) cells in SSc patients. The aim of this study was to analyse the frequency of regulatory B (Breg) cell subsets and the correlation with Tfh in SSc patients.
Methods: Circulating Breg cells CD24hiCD38hi and CD27+CD24hi levels and cTfh cells CD4+CXCR5+PD1+ were determined by cytometry in 50 SSc patients and 32 healthy subjects.
Results: The frequency of Breg cells CD24hiCD38hi and CD24hiCD27+ was significantly reduced in patients with SSc as compared to controls (p=0.02 and p<0.001, respectively). In contrast, when examining the CD21low B cell subset, the frequency was significantly increased in SSc patients compared to healthy controls, (p<0.001). There was no difference in Breg cell levels in patients with diffuse SSc and limited SSc. However, CD24hiCD27+ Breg cell frequency was significantly decreased in SSc patients with pulmonary arterial hypertension (p=0.014), but not in patients with interstitial lung disease (p=0.058). Furthermore, we observed a negative correlation between cTfh and CD24hiCD27+ Breg cell levels in SSc patients but not in healthy controls (p=0.02).
Conclusions: These results suggest that Breg cell subsets may participate in the regulation of cTfh and disease severity. Decreased CD24hiCD27+ Breg cell frequency may contribute to the development of SSc.