CLDN10 and idiopathic pulmonary fibrosis: Taken together, these results indicate that in IPF lungs, (i) club cells are undertaking active phenoconversion through which they lose typical club cell morphologies seen in mature club cells, (ii) club cells undertaking phenoconversion transmigrate from bronchiolar to alveolar areas and thereby form bronchiolized alveoli and that (iii) phenoconversion of club cells is associated with translocation of Cldn10 from lateral membrane to cytoplasm and nucleus.