Increased salivary gland tissue expression of Fas, Fas ligand, cytotoxic T lymphocyte–associated antigen 4, and programmed cell death 1 in primary Sjögren's syndrome

Abstract

Objective To assess salivary gland tissues obtained from patients with primary Sjögren's syndrome (SS) for the gene expression profile of the candidate genes TNFRSF6 (Fas), TNFSF6 (FasL), SSA1 (Ro52α and the splice variant Ro52β), SSB (La), CTLA4, PDCD1 (PD-1), and ORM2, which were selected on the basis of their putative participation in salivary gland inflammation. Methods Quantitative real-time reverse transcriptase–polymerase chain reaction (RT-PCR) was used to examine the expression of messenger RNA (mRNA). Tissue localization of the expressed proteins was detected by immunohistochemistry. Results Expression of mRNA was increased for Fas (5.1-fold; P < 0.001), FasL (8.8-fold; P < 0.05), cytotoxic T lymphocyte–associated antigen 4 (CTLA-4) (11.2-fold; P < 0.01), programmed cell death 1 (PD-1) (15.2-fold; P < 0.05), Ro52α (3.0-fold; P < 0.01), La (2.3-fold; P < 0.05), and orosomucoid 2 (ORM2) (4.4-fold; P < 0.05) in patients compared with controls when GAPDH was used as endogenous standard in duplex runs. In single runs using 2 other endogenous standards (18S and β-actin), statistically significant differences between patients and controls were confirmed for expression of Fas, FasL, CTLA-4, and PD-1, but this difference was not observed for Ro52α, La, and ORM2. Expression of Ro52β mRNA was similar in patients and controls. Conclusion The present study demonstrates a substantial increase in expression of the negative regulator molecules PD-1 and CTLA-4 and the apoptotic signal molecules Fas and FasL in patients with primary SS compared with controls, which corresponded to the immunomorphologic pattern. The results strongly indicate that these molecules have central roles in the inflammatory process in the salivary glands of patients with primary SS.