In situ correlative immuno-identification of mononuclear infiltrates and invasive bacteria in diseased gingiva

The purpose of this study was to identify and quantify mononuclear cells and invasive bacteria in consecutive histological sections in diseased gingiva. Gingival biopsies were obtained from sites displaying evidences of severe periodontitis (pocket depth greater than 5 mm, bleeding on probing) in six patients. Specimens were frozen and serially sectioned at 8 micron in a cryostat. Monoclonal antibodies (mAb) directed against membrane markers of mononuclear infiltrate cells and rabbit polyclonal sera against specific bacteria shown to be invasive in association with an immunoperoxidase technique and specific point quantification were used. The mAb panel included Leu 1 (Pan T), Leu 2a (T suppressor/cytotoxic), Leu 3a (T helper/inducer), Leu 6 (Langerhans/dendritic), Leu 7 (NK/K), Leu M3 (monocyte/macrophage), and B7 (B cell). This methodology allows for in situ per cent quantification of mononuclear cell subsets along with identification and quantification of invasive bacteria in the same gingival tissue site. This may be a practical approach to establish the relationship between bacterial invasion and cellular immune response by the host. This technique enabled the characterization of the mononuclear infiltrate in relationship to specifically identified invasive bacteria in diseased gingiva.