Functional antagonization of sTNFR-Fc against TNF-α. As described in materials and methods, TNF-α sensitive L929 cells were treated with TNF-α alone (80 ng/mL) or with TNF-α plus culture supernatants from vector-transduced cells; purified recombinant sTNFR-Fc protein (160 ng/mL) was used as a positive control. After incubation for 24 h, cell viability was then evaluated by MTT assay. Viability was significantly higher for the cells treated with conditioned medium from transduced cells expressing hTNFR-Fc (** p < 0.01 for HTB-T; *p < 0.05 for CHME-T) when compared to cultures that received TNF-α alone, or TNF-α plus culture supernatants from parental cells (CHME-N and HTB-N). Results shown represent mean levels of three independent experiments and error bars denote the standard deviation.