Down-regulation of Fas-ligand mRNA in Sjögren's syndrome patients with enlarged exocrine glands

We have reported that Sjögren's syndrome (SS) patients with enlarged exocrine glands (EEG) formerly referred to as Mikulicz's disease were defective with Fas-ligand (FasL) expression in PBL and lacrimal glands (LGs). To investigate the mechanisms of reduced FasL expression in SS patients with EEG, FasL mRNA expression level was determined using real-time PCR. The FasL gene promoter region (from -1197 to -3) was also amplified using PCR and specific primers. Expression of the FasL mRNA in the LGs and PBLs of three SS patients with EEG was significantly decreased. Direct sequencing revealed a heterozygous point mutation (-259T/C) in the FasL gene promoter region in one SS patient with EEG. A luminescent β-galactosidase (β-gal) reporter assay using a pβgal Enhancer Vector demonstrated that β-gal activity from the vector including the mutant (-259C) FasL (pβgal/mFasL) gene promoter region (735±42) was similar (p = 0.13) to that from a pβgal Enhancer Vector without the gene promoter region (603±66). On the other hand, the β-gal activity was significantly lower (p<0.0001) than that from a vector including the wild-type (-259T) FasL (pbeta;gal/wFasL) (3226±148). In conclusion, the down-regulation of FasL in SS patients with EEG may be due to transcriptional regulation, and the point mutation at -259T/C in the FasL gene promoter region may lead to the down-regulation of FasL mRNA expression and the lymphoproliferative process observed in SS patients with EEG.