Ro52- and Ro60-specific B cell pattern in the salivary glands of patients with primary Sjögren's syndrome

Abstract

Summary Primary Sjögren's syndrome (pSS) is characterized by the presence of autoantibodies against the ribonucleoprotein (RNP) particles Ro/SSA and La/SSB, and mononuclear cell infiltration of exocrine tissues, especially salivary and lachrymal glands. Low numbers of autoantigen-specific memory B cells and elevated levels of plasma cells have been detected previously in the peripheral blood (PB) of pSS patients compared to controls. As both Ro52 and Ro60-specific cells have been detected in the salivary glands (SG) of pSS patients, we aimed to characterize the SSA-specific B cell pattern in SG biopsies. A series of double immunohistochemical stainings were performed on paraffin-embedded tissue from 10 well-characterized pSS patients for each Ro52 and Ro60 along with CD19, CD5, CD20 or CD27, respectively. Ro52 and Ro60-specific cells detected in SG tissue were found to be CD19+ B cells located outside the CD19+/CD20+ B cell zones (BCZ) and also interstitially. These SSA-specific cells were also quantified. No SSA-specific cells were CD5+, indicating that they do not belong to the B-1 B cell subset. Furthermore, no SSA-specific cells were observed within the CD20+ BCZ. Hence, no SSA-specific memory B cells were detected in these individuals. Contrary to this, SSA-specific cells were found to be CD19+/CD27++, demonstrating that they are differentiating short or long-lived plasma cells. Taken together, our findings suggest that these lower levels of SSA-specific memory B cells in PB and absence of SSA-specific memory B cells in SG of pSS patients could result from activation of these cells into plasma cells at the site of inflammation.