ELEVATED SOLUBLE FAS APO-1 (CD95) LEVELS IN SILICOSIS PATIENTS WITHOUT CLINICAL SYMPTOMS OF AUTOIMMUNE-DISEASES OR MALIGNANT-TUMORS/

Soluble Fas (sFas) is produced as translation products of alternative mRNA splicing, and antagonizes the membranous Fas molecule in Fas/Fas ligand interactions. We investigated the serum sFas levels in 64 Japan ese silicosis patients with no clinical symptoms of autoimmune disease s or malignant tumours, using ELISA for sFas. The serum sFas levels in the silicosis patients were significantly higher than those in health y volunteers. Elevated serum sFas levels were also detected in patient s with systemic lupus erythematosus but, unexpectedly, no difference v ias observed in sFas levels between progressive systemic sclerosis pat ients and healthy volunteers. On the other hand, there was no signific ant difference in the expression of Fas on peripheral blood lymphocyte s between the patients with silicosis and age-matched healthy voluntee rs. These observations provided the first evidence that serum sFas lev els are elevated in silicosis patients without clinical symptoms of au toimmune diseases or malignant tumours. It remains to be clarified whe ther patients with elevated sFas levels have a tendency to develop aut oimmune diseases later, or whether some other distinct factor(s) is ne cessary to initiate the progression of autoimmune diseases.