Fig. 4. Levels (mean ± SEM) of macrophage inflammatory protein 2 (MIP-2) and interleukin 6 (IL-6) in lung lavage fluid obtained from endotoxin-treated (  gray bars ) and control animals (  black bars ). Values in nonventilated animals were obtained 24 h after treatment. The other animals underwent a 4-h period of mechanical ventilation 24 h after treatment. Irrespective of treatment, IL-6 was undetectable in most nonventilated animals (see text for details). *  P < 0.05  versus control. #  P < 0.05  versus nonventilated animals. §  P < 0.05  versus tidal volume (V^T) of 8 ml/kg.