Structure of the dermal-epidermal junction and potential mechanisms for its degradation: the possible role of inflammatory cells.

Evidence was presented indicating that the DEJ as a basement membrane is highly susceptible to degradation by a variety of neutral proteolytic enzymes with different specificities. The effect of endoglycosidases which degrade heparan sulfate was also discussed. The latter enzymes are capable of removing heparan sulfate from the DEJ, but little gross alteration of structure, such as tissue detachment, appears to result from the loss of this component. Of the proteinases discussed, PMN elastase and probably type IV collagenase are the most destructive. This is likely related to their ability to degrade the type IV collagen network. Even though proteinases with chymotrypsinlike and trypsinlike specificity were not efficient at degrading the lamina densa or removing type IV collagen from intact basement membranes, these proteinases were capable of producing epidermal detachment from the lamina densa. Many inflammatory cells of the immune system contain proteinases and endoglycosidases with the potential to degrade the DEJ and other basement membrane zones, suggesting that these cells may have a significant pathologic role in basement membrane-related diseases. PMNs and mast cells may be of particular interest because they have stored within their secretory granules high concentrations of neutral serine proteinases which have been demonstrated to degrade the DEJ.