Effects of TNF-α gene deletion and Etanercept administration on TNFα levels. TNF-α production was evaluated in the pleural exudates (a) and lung tissues (b) collected at 4 h and 24 h after carrageenan administration using a colorimetric commercial ELISA kit. A significant production TNF-α was observed in pleural exudates (a) collected from WT mice. The absence of TNF-α receptor 1 gene in mice (TNF-αR1KO) as well as the treatment of WT mice with Etanercept significantly reduced the pleural exudate production of TNF-α. Similarly, a significant increase of the TNF-α (b) was observed in the lung tissues from carrageenan-injected WT mice at 4 and 24 hours after carrageenan. In the lung tissues from carrageenan-injected TNF-αR1KO mice as well as of WT mice which have received with Etanercept the TNF-α levels were significantly reduced in comparison to those of WT animals measured in the same conditions. Data are means ± SEM of 10 mice for each group. *P < 0.01 vs. SHAM; °P < 0.01 vs. carrageenan- WT group.