Research Paper Volume 8, Issue 11 pp 3091—3109

Figure 1. Attenuation of CCSP expression in bronchiolar epithelium are associated with interstitial fibrosis and formation of fibroblastic foci in IPF lungs. Paraffin-embedded lung sections from patients with idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary fibrosis (COPD) were immunohistochemically double-labeled for club cell secretory protein (CCSP) and Claudin-10 (Cldn10). Brown and green signals correspond to CCSP and Cldn10 respectively. (A, B) Representative photomicrographs from COPD lungs display an area which shows colocalization of the two signals in bronchiolar epithelium (B). Solely Cldn10-positive club cells are seen in slightly affected alveoli (A). (C, D) Photomicrographs of highly fibrotic lesions from IPF lungs are shown. CCSP signals are scarcely scattered. Dashed-line in (C) denotes a distinct area with CCSP- and/or Cldn10-positve club cells having occluded a bronchiolar lumen. Arrows in (D) denote club cells blended with the surrounding fibrotic interstitium. (E, F) Photomicrographs of a widely open bronchiolar lumen and surrounding fibrotic interstitium from IPF lungs are shown. Dashed-line in (E) denotes an area with club cell hypercellularity. Area circled by dot-dashed line (FF) denotes fibroblastic foci. Luminal side of fibroblastic foci is lined by CCSP-negative Cldn10-positive club cells (E) whereas the adjacent bronchiolar epithelium exhibits both signals (F). Original magnifications: x40 (A, C, E); x400 (B, D, F).