T-CELL RECEPTOR GAMMA-DELTA-EXPRESSING INTRAEPITHELIAL LYMPHOCYTES ARE PRESENT IN NORMAL AND CHRONICALLY INFLAMED HUMAN GINGIVA

The phenotypic profile of leucocytes in diseased and normal gingival t issue was studied in situ and in isolated gingival mononuclear cell (G MC) preparations. T-cell receptor (TcR)gammadelta+ cells showed prefer ential localization to epithelium, both in normal and inflamed gingiva , and were present in crevicular as well as oral epithelium. In normal gingiva greater-than-or-equal-to 30% of the isolated leucocytes expre ssed TcRgammadelta, of which the majority were CD4- CD8-, and expresse d CD45RA. The proportion of TcRgammadelta+ cells in GMC from periodont itis tissue varied between 2 and 32%. In contrast to normal gingiva th e majority of TcRgammadelta+ cells in diseased tissue were CD8+ and ex pressed CD45RO. Thus expression of the CD8 antigen on gingival TcRgamm adelta+ cells is probably a consequence of immune activation. Numerous Langerhans' cells and keratinocytes expressing the major histocompati bility complex (MHC) class I-like antigen, CD1, were present within no rmal and inflamed gingival epithelium in close proximity to the TcRgam madelta+ cells. Most CD1a+ cells were scattered within oral epithelium . CD1c+ cells were localized close to the basal layer of crevicular ep ithelium. No CD1b+ cells were found. TcRalphabeta+ cells, CD4+ and B c ells were restricted to lamina propria of periodontitis lesions. The p resence of intraepithelial TcRgammadelta+ cells in normal gingiva sugg ests that they constitute the 'first line of defence' against the pote ntially harmful microflora in the oral cavity. Induction of CD8 and CD 45RO antigens on TcRgammadelta+ cells in periodontitis tissue indicate that they play a significant role in the disease. CD1 molecules on La ngerhans' cells and keratinocytes may be the restriction elements for the CD8+ TcRgammadelta+ cells.