Elevated soluble Fas in aqueous humor of patients with Behcet's uveitis: correlation with uveitis severity

PURPOSE: To examine the role of soluble Fas (sFas) in patients with Behcet's uveitis. METHODS: We measured the sFas levels in both sera and aqueous humor (AH) of patients (n = 40) with uveitis and of non-uveitis controls (n = 27) using an enzyme-linked immunosorbent assay. The patients with uveitis comprised 24 with Behcet's disease, 6 pan-uveitis, 5 anterior uveitis, 2 lens-induced uveitis, 1 Vogt-Koyanagi-Harada disease, 1 sarcoidosis, and 1 retinal vasculitis. The severity of uveitis was determined by the Hogan grading method (0--4 grade) at the time of sampling. RESULTS: The concentration of aqueous sFas in uveitis patients was significantly higher than that in non-uveitis controls, while there was no difference in the serum concentration of sFas between the two groups. In the paired samples of serum and AH, obtained simultaneously, the aqueous sFas levels were higher than serum Fas levels in patients with uveitis, whereas the non-uveitis controls displayed significantly lower sFas levels in AH than in the serum. The sFas levels in AH or serum were not different between Behcet's uveitis patients and non-Behcet's uveitis patients. However, in patients with Behcet's uveitis, circulating sFas strongly correlated with aqueous sFas, which was not so in those with non-Behcet's uveitis. Patients (n = 29) with more active (grade greater-than-or-equal 2) uveitis had significantly higher levels of aqueous sFas than those (n = 11) with less active (grade < 2) uveitis. After treatment with steroids and/or immunosuppressive agents, aqueous sFas levels decreased in parallel with a reduction in the number of inflammatory cells. CONCLUSIONS: The levels of sFas were elevated in patients with Behcet's uveitis and correlated well with the uveitis severity in these patients.