Attenuated apoptosis of B cell activating factor-expressing cells in primary Sjögren's syndrome

Abstract

B cell activating factor (BAFF) is known to be a powerful regulator of B-cell differentiation and proliferation. The aim of this study was to assess the incidence of apoptosis among BAFF-expressing cells in Sjögren's syndrome (SS) salivary gland tissue. We performed double stainings of BAFF together with one of the markers, CD21, CD68, CD40, Fas, Bcl-2 or Bax, and monitored apoptosis among BAFF expressing cells by using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling method. A significantly lower level of apoptosis among the BAFF-expressing cells was detected in salivary glands from patients with SS compared with controls (p = 0.03). Furthermore, no difference in the coexpression of Fas or CD40 together with BAFF was detected between patients and controls. Coexpression of the pro apoptotic molecule Bax together with BAFF was nonsignificantly decreased in patients with SS compared with controls. Our results suggest that a reduced level of apoptosis among BAFF-expressing cells might lead to longer-existing BAFF expression within these cells and thereby maintain signaling for tissue-infiltrating B cells to proliferate and mature.