CLDN10 and idiopathic pulmonary fibrosis: To confirm that (i) IPF lungs encompass Cldn10-positive club cells that have lost club cell morphology to a certain extent and that (ii) club cells undertaking phenoconversion exhibit cytoplasmic and/or nuclear expression of Cldn10, we probed IPF lung sections for Cldn10 using immunogold labeling method and observed the stained sections under transmission electron microscope (TEM).