Airway Epithelial cells Sample Clauses

Airway Epithelial cells. The epithelium of the lung is the first point of contact for inhaled pollutants, airborne allergens, and microorganisms (Bals & Xxxxxxxx 2004). It plays an active role in immunity, through environmental sensing and pathogen detection, signalling to modulate both innate and adaptive immune responses, and direct antimicrobial activities (Xxxx & Xxxxxxxxx 2007). The airway epithelium is pseudostratified, columnar, or cuboidal, and consists mostly of ciliated, undifferentiated, secretory and basal cells (Xxxxxxx et al. 2008). The airway epithelium lies on a basement membrane, which provides an anchor to facilitate adhesion and migration of epithelial cells, regulates their phenotype and polarity, and separates them from the underlying mesenchymal tissue (Knight & Holgate 2003). Infiltrating inflammatory and immune cells can move freely through this membrane and between epithelial cells (Xxxxxx & Xxxxxxx 2003). The airway epithelium plays a vital role in protecting the human body from foreign particles. The tight junctions that fasten together epithelial cells prevent the passage of molecules between adjacent cells, forming a physical barrier that protects underlying tissues (Xxxxxxxxxxxx & Xxxxx 1984). The mucociliary elevator system, consisting of mucus-secreting and ciliated cells, functions to effectively clear inhaled pollutants, allergens and microbes from the lungs (Mall 2008). Recognition of inhaled particles by epithelial cells leads them to secrete mediators such as chemokines and cytokines to attract professional immune cells, but some of their secretions also show direct antimicrobial activity. These include short antimicrobial peptides such as defensins, and larger proteins such as lysozyme and lactoferrin (Xxxxxxxx 2001).