CLDN5 and chronic obstructive pulmonary disease: First, we compared healthy and diseased peri-bronchial and alveolar non-epithelial cells and found the increase in T lymphocytes in both COPD compartments, and NK cells in peri-bronchial, with a decrease in CLDN5 endothelial and RGCC fibroblasts in alveolar compartments (Supplementary Fig. 15A).