The distribution of adhesive mechanisms in the normal bronchial epithelium

The integrity of the bronchial epithelium is dependent on various adhesion mechanisms that serve to hold the composite structure of the epithelium together and anchor it to the underlying basement membrane. Using immunohistochemistry we wanted to map out a number of these junctional and non-junctional adhesion mechanisms in the normal human bronchial epithelium. The beta 1-associated integrin subunit alpha 2 was immunolocalized to all of the epithelial intercellular spaces, whilst alpha 6 and beta 4 were strongly evident at the basal cell layer basement membrane junction. The alpha 1 and alpha 5 integrin subunits were not detected anywhere in the epithelium. Monoclonal antibodies (MoAbs) to tight junction polypeptides and the E-cadherin, liver cell adhesion molecule (LCAM), immunolocalized to the apicolateral portions of the intercellular junctions between all neighbouring columnar cells, with LCAM extending further along the lateral cell membrane. Desmosomal protein (dp) 1 and 2 MoAbs gave a punctate pattern between all of the suprabasal cells, and exhibited the greatest intensity of staining at the junction between the columnar and basal cell layers. In conclusion, there is an organized distribution of adhesive mechanisms within the normal human bronchial epithelium, which may be targeted by the various insults which lead to epithelial shedding.