Detection of soluble FasL in the culture supernatants of tumor cells.

One million cells were cultured in 0.2 mL medium for 24 hours, and the supernatant was harvested and centrifuged. Culture supernatants from COS-C (transfected with control plasmid) and COS-FasL (transfected with FasL cDNA), LSA, EL-4, and L1210 tumor cells and from PE-9 T cells were tested in the ELISA assay to detect the presence of soluble FasL. The concentration of sFasL was calculated based on the use of purified sFasL as a standard.