Fig. 6.

Apoptosis-inducing activities of recombinant wild-type and mutant FasL proteins secreted by COS cells. COS cells were transfected with pME18S empty vector, pME18S carrying the full-length human FasL cDNA, or FasL constructs carrying point mutants. The culture supernatants were recovered 52 h after transfection and assayed for sFasL by ELISA. Cytotoxic activity of the mutant sFasL was determined per ng of protein. Fas-expressing Jurkat-NU cells were cultured with the supernatants containing wild-type and mutant sFasL proteins for 24 h. Cell death was then estimated by DNA staining with PI. Data shown are representative of three independent experiments. ▪, Soluble FasL 0 ng/ml; , 0·8 ng/ml; , 1·6 ng/ml; , 3·2 ng/ml.