C5a-induced alveolitis in WT and proCPB^−/− mice. C5a at 2 concentrations or saline control (vehicle) were instilled endotracheally in WT (□) or proCPB^−/− (▪) mice. Six hours later, BAL was performed, and total WBC counts (A) and total protein contents (B) in the BAL fluids were determined. (C) The wet-to-dry weight ratio of the right upper lobe was determined as described in “Materials and Methods” (n = 6 in each group; ** P < .05). Data are presented as mean ± SD.