Bronchoalveolar differential cell counts following sequential application of LPS and fMLP in BALB/c and C57BL/6 mice. Animals were intranasally challenged with LPS (0.3 mg/kg intranasally) or PBS (50 μl). Twenty four hours after the challenge, mice were intranasally challenged with increasing concentrations of fMLP (0.5–5 mg/kg) or 50 μl of vehicle (1% DMSO in PBS). Two hours after the second challenge, animals were sacrificed and bronchoalveolar lavage performed. Data are expressed as mean ± SEM from 5–9 mice per groups. Significance (P < 0.05), indicated by (*) or (#) is versus PBS-challenged/Vehicle-treated mice and LPS-challenged/Vehicle-treated mice, respectively.