PPIG and hypersensitivity pneumonitis: Unlike the allergic pneumonitis-only group, which is classically influenced by the Th2 response, the airway neutrophilic inflammation observed in the allergic/CYP-exposed group might be attributed to further oxidative stress induced by CYP exposure that shifts the immune reactivity to INF-γ/Th-17 axis and p38 MAPK activation.