Without prior neonatal OVA exposure, repetitive adulthood OVA inhalation was unable to induce asthma development in terms of the absence from any substantial alterations of AHR, airway resistance, lung histology, as well as intrapulmonary expressions of relevant genes (Gob5/MUC5AC, cytokines, and chemokines), but remained sufficient to elicit the generation of serum OVA-IgE and IL-5 secreting Th2 cells. This evidence concerns the gene MUC5AC and asthma.