Increased elafin expression in cystic, dysplastic and neoplastic oral tissues.

Expression of human leukocyte elastase inhibitor, elafin, otherwise known as skin-derived antileukoproteinase inhibitor (SKALP), was investigated in normal and abnormal oral tissues using a specific anti-SKALP rabbit antiserum. Weak staining was observed in keratinizing epithelia of normal oral mucosa but not in non-keratinizing mucosa. Increased expression was also observed in the suprabasal layers of dysplastic oral epithelia and in well-differentiated squamous cell carcinoma, but not in basal cell carcinoma. A uniform strong expression was observed in all supra-basal layers of odontogenic keratocyst epithelia, except in regions where inflammatory infiltrate was adjacent to keratocyst epithelia. In contrast, elafin expression in a small number of dentigerous cysts and ameloblastomas was more patchy. The increased levels of elafin in keratocyst epithelia and dysplastic tissue may be a cellular homoeostatic response to generate a protective barrier preventing proteolytic degradation of underlying elastic tissue.