Increased total cell counts in BAL fluid from SP-A^–/– mice. Lung cells were recovered by BAL, stained with trypan blue, and counted under light microscopy. (a) The low dose of RSV (10⁶ pfu) caused less migration of inflammatory cells in the lungs from both genotypes; however, an earlier influx of cells was found in SP-A^–/– (filled bars) BAL fluid than in SP-A^+/+ (hatched bars) mice. (b) SP-A^–/– mice infected with 10⁷ pfu RSV had significantly greater total cell counts in BAL fluid at all time points. Data are mean ± SEM with n = 5 mice per group (a) and n = 9 mice per group (b). *P < 0.05 compared with SP-A^+/+ mice.