['It is now considered that the major component of mucus, MUC5AC, is mainly produced by goblet cells but not submucosal glands, and the role of the submucosal glands in the production of MUC5AC is unclear. The aim of this study was to clarify whether human submucosal glands produce MUC5AC.', 'Immunohistochemical analysis with MUC5AC antibody of lower airways resected from six lung cancer patients and three patients with acute myocardial infarction was performed.', 'The submucosal glands contained both MUC5AC-positive cells and non-positive cells.'] Do submucosal gland cells in human lower airways produce MUC5AC protein?