Human Tracheal Gland (HTG) cells are primary cells isolated from human tracheal submucosal glands. These cells are crucial for studying the mechanisms of airway secretion and the composition and regulation of glandular secretions, which play a significant role in lung defense mechanisms. In culture, HTG cells can retain immunocytochemical, ultrastructural, and functional features of both differentiated serous and mucous gland cells, making them a valuable model for investigating the biology and pathology of human tracheobronchial submucosal glands, particularly in conditions like cystic fibrosis and chronic bronchitis where mucus hypersecretion is a key feature.