Lung epithelial cells in the defense against tuberculosis: an essential neglected activity

The human lungs are perpetually exposed to a myriad of potential pathogens that necessitate neutralization and elimination. Within the airways, innate immune mechanisms are employed to achieve this objective. A pivotal mechanism is the epithelial cell barrier, which encompasses nearly the entirety of the pulmonary area and the respiratory tract. The cellular variability within the respiratory tract is significant not only structurally but also functionally. For instance, the epithelial barrier is composed of different cell types, while some participate mainly in gas exchange, such as type 1 pneumocytes, other cell types are mainly responsible for the production of pulmonary surfactants and serve as the first line of defense against xenobiotics and pathogens, such as type 2 pneumocytes. The immunological defense mechanisms associated with the epithelial barrier include the secretion of mucus, chemokines, cytokines, and antimicrobial peptides, among others. The functionality of these epithelial cells is crucial for maintaining respiratory health; however, external factors such as pathogens can disrupt their operations, leading to diseases like tuberculosis-a global health concern due to its high morbidity and mortality rates. This review briefly examines the immunological pathways associated with the epithelial cell barrier and explores factors that interfere with their function, with a focus on tuberculosis disease.