Host upper respiratory tract epithelial cells and local immune cells

This entry describes the integrated cellular and ecological system of the upper respiratory tract (URT), which serves as the primary portal of entry and first line of defense for inhaled pathogens. It encompasses a diverse population of epithelial cells—including ciliated, goblet, and basal cells—working in concert with local immune cells such as macrophages, dendritic cells, and intraepithelial lymphocytes (1). The interaction between these cells is critical for maintaining the mucosal barrier, executing mucociliary clearance, and initiating innate and adaptive immune responses (2). In the context of respiratory infections like COVID-19 or influenza, this environment is the site of initial viral replication and subsequent inflammatory signaling (3). While not a single molecular target, pharmacological strategies often focus on this niche to deliver localized treatments that reduce inflammation or enhance mucosal immunity (4). (1) Gohy et al., 2019, European Respiratory Review; (2) Mudd et al., 2020, Science Immunology; (3) Hou et al., 2020, Cell; (4) Pires et al., 2009, Journal of Pharmacy & Pharmaceutical Sciences.

Other names

Upper respiratory tract mucosaURT epithelial-immune axisNasopharyngeal microenvironmentMucosal immune system of the upper airway

Therapeutic agents act by modulating local inflammatory pathways, enhancing physical barrier integrity, or inducing site-specific mucosal immune memory (e.g., secretory IgA production).