Objective: Interactions of the FAS with FAS ligand have been proposed as a major regulatory mechanism of immune homeostasis. Soluble FAS (sFAS) acts as a competitive antagonist to FAS, thereby inhibiting FAS mediated apoptosis. sFAS concentrations have been studied in various autoimmune diseases, with controversial results. In this cross sectional study, we investigated the role of sFAS protein in attack-free patients with familial Mediterranean fever (FMF) with and without amyloidosis.
Methods: Twelve FMF patients without amyloidosis (male/female: 7/5; median age 23.5 yrs, range 17-38), 10 FMF patients with amyloidosis (male/female: 5/5; median age 41.5 yrs, range 33-51), and 14 controls (male/female: 6/8; median age 46 yrs, range 38-57) were enrolled in the study. Serum sFAS concentrations were studied by ELISA.
Results: Median serum sFAS concentrations were 4630 (2580-12,270), 1338 (453-3240), and 3430 (2110-5960) pg/ml in FMF patients without amyloidosis, FMF patients with amyloidosis, and controls, respectively. Intergroup differences were all statistically significant (p < 0.05).
Conclusion: Elevated serum sFAS concentrations in attack-free FMF patients might be due to dysregulated apoptosis of polymorphonuclear leukocytes together with the ongoing subclinical inflammatory activity. On the other hand, decreased sFAS concentrations could contribute to the augmented apoptosis together with the alterations in immune response leading to the amyloidosis.