Immunohistologic and morphometric analysis of cytotoxic T lymphocytes in gingivitis

Background: Gingivitis is an inflammatory phenomenon localized in gingival tissues and histologically characterized by an infiltration of several infl ammatory cell populations. The purpose of this study was to characterize, l ocalize, and quantify in situ inflammatory and cytotoxic T lymphocytes usin g immunolabeled gingival tissue sections in order to specify their implicat ion during human gingivitis, since it is well known that such cells play an important role in the defense against bacterial elements. Methods: Paraffin gingival tissue sections from T patients with gingivitis (G) and from 7 clinically and histologically healthy controls (C) were immu nohistochemically stained by specific antibodies (anti-CD45, anti-CD3, anti -CD8, anti-CD20, anti-TIA-1, anti-GrB, and anti-CD68), allowing the quantif ication of inflammatory cells in upper gingival epithelium (Ep), in the bas al epithelium layer (BEp), and in upper connective tissue (CT). Collagen fi bers were stained by sirius red F3Ba in order to evaluate, by morphometric and automated image analysis, the surface occupied by collagen bundles and to histologically confirm the absence of pathology of the clinically select ed healthy controls. Results: In the gingivitis group, CD45+, CD3+, CD8+, TIA-1+, and GrB+ lymph ocyte numbers were significantly increased in Ep (P <0.05); and CD45+, CD3, and TIA-1+ lymphocyte numbers were significantly increased in BEp (P <0.0 5) compared respectively to Ep and BEp of group C. In Ep of group G, mean C D8+/CD3+ cell ratio was significantly increased (P <0.05) compared to BEp a nd CT, and 25% of TIA-1+ cytotoxic cells were activated GrB+ cells. Conclusions: The present study suggests that intraepithelial cytotoxic T ly mphocytes play an important role during gingivitis and CD8 expression and t hat activation of TIA-1+ cytotoxic cells could be induced in Ep in response to epithelial environment. Thus, gingival epithelial tissue, which is gene rally only considered as a physical barrier, in fact contains numerous immu ne cell populations preventing the infiltration of pathogenic elements into the connective tissue. Particular clinical attention must be taken for the preservation of the epithelial tissue integrity.