Immunopathology of a two-hit murine model of acid aspiration lung injury

In a two-hit model of acid aspiration lung injury, mice were subjected to n onlethal cecal ligation and puncture (CLP). After 48 h, intratracheal (IT) acid was administered, and mice were killed at several time points. Recruit ment of neutrophils in response to acid was documented by myeloperoxidase a ssay and neutrophil counts in bronchoalveolar lavage (BAL) fluid and peaked at 8 h post-IT injection. Albumin in BAL fluid, an indicator of lung injur y, also peaked at 8 h. When the contributions of the two kits were compared , neutrophil recruitment and lung injury occurred in response to acid but w ere not greatly influenced by addition of another hit. Neutrophil sequestra tion was preceded by elevations in KC and macrophage inflammatory protein-2 alpha in plasma and BAL fluid. KC levels in BAL fluid were higher and peak ed earlier than macrophage inflammatory protein-2 alpha levels. When KC was blocked with specific antiserum, neutrophil recruitment was significantly reduced, whereas albumin in BAL fluid was not affected. In conclusion, muri ne KC mediated neutrophil recruitment but not lung injury in a two-hit mode l of aspiration lung injury.