Highly sensitive ELISA for soluble Fas in serum: Increased soluble Fas in the elderly

We have developed and characterized a highly sensitive ELISA for soluble Fas (sFas) in the serum. The linearity of calibrator range was 0.06-2.00 μg/L and the detection limit was 0.01 μg/L. The average within- and between-run CVs were 3.9% and 3.8%, respectively. The recovery of added sfas to serum was 93-118%. The effects of possible interferences (tryglyceride, hemoglobin, bilirubin) were negligible. We determined serum sfas in 155 healthy subjects, ages 20-69. The mean value of sfas in men (2.50 ± 0.63 μg/L, n = 78) was significantly higher than that in women (2.01 ± 0.53 μg/L, n = 77) (P < 0.001). Furthermore, there was a significant correlation between serum sfas concentration and age (men, r = 0.397, P < 0.001; women, r = 0.569, P < 0.001). Although the concentrations of sfas tended to increase with aging, it remains to be clarified how Fas-mediated apoptosis relates to aging.