The goal of this study was to determine whether Fas deficiency is protective in mechanically ventilated mice exposed to intratracheal LPS. The main finding was that Fas-deficient lpr mice showed decreased neutrophil recruitment in response to combined mechanical ventilation and LPS, even though the cytokine, permeability, and apoptotic responses were similar to those of B6 mice. Interestingly, despite the presence of similar concentrations of KC in the BAL of lpr and B6 mice, only the B6 mice showed extensive KC deposition in the lungs, and this was associated with the presence of anti-KC:KC complexes in the BALF and lung tissue.