CD40, CD154, Bax and Bcl-2 Expression in Sjögren's Syndrome Salivary Glands: a Putative Anti-Apoptotic Role During its Effector Phases

Abstract

Sjögren's syndrome (SS) is an autoimmune rheumatic disorder characterized by chronic lymphocytic infiltration and decreased secretion in the salivary glands (SGs). For some time, apoptosis has been suggested to constitute the major mechanism for acinar epithelial destruction during the effector phases; however, this is still controversial. We have recently demonstrated that despite the expression of Fas and FasL, the incidence of apoptosis is not increased in SS patients compared with control individuals. Our aim was therefore to further evaluate the expression of the pro- and anti-apoptotic Bax and Bcl-2 proteins. CD40 and CD154 expression was also investigated, as CD40 ligation has been suggested to protect cells from Fas-mediated apoptosis. Immunohistochemical staining was performed on SG tissue from primary and secondary SS patients, a group of patients with non-SS-related degenerative changes as well as on healthy control individuals. The frequency of stained cells in the foci of infiltrating mononuclear cells (IMCs) and in the acinar and ductal epithelium was determined. We found the expression of Bcl-2 but rarely Bax in SS SG IMCs. Bcl-2 in epithelial cells was sparse, while Bax expression occurred frequently and with no significant difference between the patient groups. CD40 and CD154 expression was high among SS IMCs, while CD40 levels were slightly decreased in SS epithelium compared with controls. Elevated CD154 expression was found in SS epithelium, being significantly increased in the ducts. In conclusion, our study further supports the hypothesis about apoptosis resistance among SS focal IMCs and suggests a putative protective role of CD40 ligation in SS SG epithelium.