The histopathological characteristics of ITO and In2O3 rat models were: (a) interstitial fibrosis and lymphocytic infiltration; (b) intraalveolar eosinophilic exudates characteristic of pulmonary alveolar proteinosis and numerous cholesterol clefts and giant cells containing brown particles; (c) focal eosinophilic exudates with immunoreactive SP-A, SP-D, KL-6, and GM-CSF; and (d) inflammatory infiltrated peribronchiolar fibrosis with immunoreactive NF-κB p65 and HO-1. Here, MUC1 is linked to pulmonary alveolar proteinosis.