CELLULAR AND MOLECULAR MECHANISMS OF BACTERIAL ADHESION TO RESPIRATORY MUCOSA

Different bacterial species adhere avidly to respiratory mucus. Such a dhesion, when followed by ciliary clearance, represents an important s tage of the airway defence system. However, in pathological conditions , the mucociliary clearance may be severely reduced, and mucus-associa ted bacteria may multiply and infect the underlying epithelium. Only a few bacteria have been shown to adhere to ciliary membranes of functi onally active ciliated celts. Therefore, the first way in which most o f the respiratory pathogens associate with the airway epithelium is li kely to be by their adhesion to mucus. Some bacteria also secrete prod ucts that may affect ciliary function and/or cause cell death and epit helial disruption. Respiratory pathogens that do not bind to normal ci liated cells may readily adhere to injured epithelial cells, or to the unmasked extracellular matrix. Furthermore, following injury, epithel ial respiratory cells in the process of migration, in order to repair the wounds, may present receptors to which bacteria adhere. The adhesi on to all of these epithelial receptors may contribute to the chronici ty of many bacterial respiratory infections.