New aspects of the role of Fas receptor and Fas Ligand in patients with Sjögren’s syndrome

Abstract Background: Sjögren’s syndrome patients, like other patients with autoimmune disorders, display dysregulation in the function of their immune system. Fas and Fas Ligand (FasL) belong among dysregulated proteins. Although they have been long studied, there are still several unknown aspects of biological importance of Fas and FasL. Methods: In patients with Sjögren’s syndrome and age-matched healthy individuals, we studied Fas and FasL on IL-2Rα+ cells and in serum using flow cytometry and enzyme-linked immunosorbent assay, respectively. We also measured the expression of Bcl-2 and Bax by reverse transcription quantitative real-time PCR (RT-qPCR) and percentage of apoptotic and dead cells using Annexin V and 7-AAD staining in lymphocytes. Results: FasL was increased in patients’ T and B cells and serum while Fas was increased in patients’ monocytes, T and B cells. No signs of increased apoptosis were found. We suspect an effect of non-steroidal anti-inflammatory therapy on the percentage of Fas+ B cells which decreased with the therapy in our patients. In the healthy individuals, there was a noticeable pattern in the expression of Fas which was mutually correlated between populations of mononuclear cells; this correlation was absent in the patients with Sjögren’s syndrome. Conclusions: The increased expression of Fas in IL-2Rα+ lymphocytes does not increase the apoptosis of lymphocytes. These lymphocytes increase the expression of FasL and may induce apoptosis in other cells. The lack of correlation for the expression of FasL in Sjögren’s syndrome patients may suggest a loss of regulation.