Immunofluorescence staining of bronchial epithelium spheroids. I and II) Right panels of immunostained BES using antibodies specific to various cells types and intercellular junction proteins. Left panels show bright field images. (A) Anti-cytokeratin 13 antibody (CK13) for basal cells. (B) Anti-cytokeratin 18 (CK18) for ciliated cells. (C) Anti-mucin 5AC (MUC5AC) for secreted cells. (D,E,F) Antibodies against intercellular junction proteins zonula occludens-1 (ZO-1), Occludin (Occl) and E-Cadherin (E-Cad). Arrows depict staining for ZO-1 and Occludin in the intercellular junctions. Micrographs are representative of spheroids from COPD and non-COPD patients (n = 7).