Reversibility of airway hyperreactivity and goblet cell hyperplasia after allergen challenge. (a) On the indicated study days, wild-type mice were sensitized to Ova, then challenged with intranasal PBS or Ova either twice on day 0 (Ova ×2) or twice on day 0 and again on days 1 and 2 (Ova ×4), and finally were phenotyped for airway hyperreactivity and goblet cell hyperplasia. (b) For each experimental condition, airway reactivity was assessed as described in legends for Figure 3 and Figure 5. (c) For the same conditions, lung sections were immunostained for MUC5AC mucin, and immunopositive cells were quantified as described in Figure 4 legend. For b and c, all values represent mean ± SEM for groups of eight to ten mice. *Significant change from the corresponding PBS-challenged cohort.