During the transition between acute (3 d) and chronic (7 d) empyema in rabbits (Figure 1, panel (a)), the levels of inflammatory markers TNF-α, IL-6, IL-8, and IL-1 β in the pleural fluid at baseline decreased by 2.5, 57, 2.1, and more than 100-fold, respectively. Here, IL6 is linked to empyema.