T-cell receptor gamma delta-expressing intraepithelial lymphocytes are present in normal and chronically inflamed...

The phenotypic profile of leucocytes in diseased and normal gingival tissue was studied in situ and in isolated gingival mononuclear cell (GMC) preparations. T-cell receptor (TcR)gamma delta + cells showed preferential localization to epithelium, both in normal and inflamed gingiva, and were present in crevicular as well as oral epithelium. In normal gingiva > or = 30% of the isolated leucocytes expressed TcR gamma delta, of which the majority were CD4- CD8-, and expressed CD45RA. The proportion of TcR gamma delta + cells in GMC from periodontitis tissue varied between 2 and 32%. In contrast to normal gingiva the majority of TcR gamma delta + cells in diseased tissue were CD8+ and expressed CD45RO. Thus expression of the CD8 antigen on gingival TcR gamma delta + cells is probably a consequence of immune activation. Numerous Langerhans' cells and keratinocytes expressing the major histocompatibility complex (MHC) class I-like antigen, CD1, were present within normal and inflamed gingival epithelium in close proximity to the TcR gamma delta + cells. Most CD1a+ cells were scattered within oral epithelium. CD1c+ cells were localized close to the basal layer of crevicular epithelium. No CD1b+ cells were found. TcR alpha beta + cells, CD4+ and B cells were restricted to lamina propria of periodontitis lesions. The presence of intraepithelial TcR gamma delta + cells in normal gingiva suggests that they constitute the 'first line of defence' against the potentially harmful microflora in the oral cavity. Induction of CD8 and CD45RO antigens on TcR gamma delta + cells in periodontitis tissue indicate that they play a significant role in the disease. CD1 molecules on Langerhans' cells and keratinocytes may be the restriction elements for the CD8+ TcR gamma delta + cells.