A: effect of Muc5b genotype on levels of Muc5b in BAL. Solid bars, WT mice; gray bars, Muc5b+/− mice; striped bars, Muc5b−/− mice (n = 6 each genotype; 5 wk old). The level of Muc5b was significantly reduced in the Muc5b−/− animals compared with WT (*P ≤ 0.05). B: effect of Muc5b genotype on MCC. Solid bars, WT mice (n = 3); gray bars, Muc5b+/− mice (n = 10); striped bars, Muc5b−/− mice (n = 6). All animals were 6 mo old. ANOVA indicated statistical difference (*P ≤ 0.05) from WT and each genotype from the other (*P ≤ 0.05).