Yüksel H.Tunca S.2024-07-222024-07-22202221688362http://akademikarsiv.cbu.edu.tr:4000/handle/123456789/12984When the organism encounters a foreign substance, it responds with mutual and regular interactions at different stages of the immune system. In airway diseases, the first encounter is at the epithelial level, where innate immune cells and their responses form the first leg of the protective mechanism. The most important barrier for environmental damage is the epithelial barrier. However, the epithelial barrier is not just a mechanical barrier. The formation of the microbiome on the epithelium and the tolerance or intolerance to environmental factors are vital. This vital balance is maintained between the epithelial surface and the subepithelial innate immune system. This is achieved by the epithelial line, which is a mechanical and functional barrier between them. In this respect, epithelial barrier function preservation has an important role in the development and prognosis of airway disease. © 2021 Taylor & Francis Group, LLC.EnglishAll Open Access; Green Open AccessEpitheliumImmune Systemactinallergencadherinepidermal growth factor receptorimmunoglobulin Einterleukin 1interleukin 6transforming growth factor betaadaptive immunityairway epithelium cellairway remodelingasthmabasolateral membraneblood brain barriercell membranecell migrationcytokine productionenzyme stabilityepithelial mesenchymal transitionepitheliumhumanimmune responseimmune systemimmunocompetent cellimmunopathologyinnate immunityprognosisrespiratory tract diseaseReviewSARS coronavirusepitheliumReview10.1080/21688370.2021.2020706