Gingival keratinocytes express HLA-DR antigens in chronic gingivitis

The expression of the histocompatibility antigens HLA-DR and HLA-A, B, C within periodontally diseased tissue was investigated using immunohistological and histochemical techniques. Tissue was obtained from 18 patients with periodontal disease and from 2 healthy volunteers. HLA-DR antigen was expressed by the keratinocytes of the oral epithelium in all inflamed samples but was not a feature of normal tissue where HLA-DR reactivity was confined to Langerhans cells. These results are consistent with an underlying cellular immune process. Using a variety of phenotypic markers it was possible to characterize the macrophage population within the connective tissue into 2 distinct types: an antigen-presenting cell type located subjacent to the oral epithelium and a phagocytic cell type situated deep within the connective tissue.