Decreased BAFF Receptor Expression and Unaltered B Cell Receptor Signaling in Circulating B Cells from Primary Sjögren’s Syndrome Patients at Diagnosis

Abstract

Animal models of autoimmunity and human genetic association studies indicate that the dysregulation of B-cell receptor (BCR) signaling is an important driver of autoimmunity. We previously showed that in circulating B cells from primary Sjögren’s syndrome (pSS) patients with high systemic disease activity, protein expression of the BCR signaling molecule Bruton’s tyrosine kinase (BTK) was increased and correlated with T-cell infiltration in the target organ. We hypothesized that these alterations could be driven by increased B-cell activating factor (BAFF) levels in pSS. Here, we investigated whether altered BCR signaling was already present at diagnosis and distinguished pSS from non-SS sicca patients. Using (phospho-)flow cytometry, we quantified the phosphorylation of BCR signaling molecules, and investigated BTK and BAFF receptor (BAFFR) expression in circulating B cell subsets in an inception cohort of non-SS sicca and pSS patients, as well as healthy controls (HCs). We found that both BTK protein levels and BCR signaling activity were comparable among groups. Interestingly, BAFFR expression was significantly downregulated in pSS, but not in non-SS sicca patients, compared with HCs, and correlated with pSS-associated alterations in B cell subsets. These data indicate reduced BAFFR expression as a possible sign of early B cell involvement and a diagnostic marker for pSS.

Editorial for Special Issue “Advances in the Pathogenesis and Treatment of Immune-Mediated Inflammatory Diseases”

“…Merino Vico et al review the current literature and highlight the importance of these cells in ANCA-associated vasculitis [ 1 ]. In an original article, Neys et al investigated potential alterations in BAFF receptor expression and BCR signaling in B cells of patients with primary Sjogren’s syndrome (pSS) at diagnosis [ 2 ]. Using (phospho-)flow cytometry, the phosphorylation of BCR signaling molecules and BAFF receptor (BAFFR) expression was quantified in circulating B cell subsets of pSS patients compared to non-pSS sicca and healthy controls (HCs).…”