TNF and empyema: Notably, while levels of total PAI-1, TNF-α, IL-6, IL-8 (Figure 1, panel (c)), and IL-1 β (below level of detection), at baseline in chronic empyema were lower (p < 0.05) than those in the acute stage, the level of active PAI-1 did not change significantly, and the level of TGF-β was elevated (p < 0.05) when compared to baseline in acute empyema in rabbits [41] (Figure 1, panel (c)).