IN-SITU DETECTION OF APOPTOSIS AT SITES OF CHRONIC BACTERIALLY INDUCED INFLAMMATION IN HUMAN GINGIVA

Apoptosis is a key phenomenon in the regulation of the life span of te rminally differentiated leukocytes. Human gingiva represents an establ ished model to study Immune responses to bacterial infection. In this investigation, we used the TUNEL (terminal deoxynucleotidyltransferase -mediated dUTP-biotin nick end labeling) technique to evaluate presenc e and topographic location of apoptosis-associated DNA damage in human gingival biopsies along with the expression of the p53 and Bcl-2 apop tosis-regulating proteins. Qualitative data analysis showed high densi ties of cells expressing DNA damage and p53 both within the epithelial attachment to the tooth and in the perivascular infiltrate (infiltrat ed connective tissue [ICT]) immediately underlying the site of chronic bacterial aggression. Topographic consistency between DNA damage- and p53-positive cells was consistently observed. Quantitative analysis o f the ICT showed mean densities of DNA damage- and p53-positive cells of 345 +/- 278 and 403 +/- 182 cells/mm(2), respectively. Numerical co nsistency was confirmed by multivariate regression analysis: densities of DNA damage-positive cells were significantly predicted by densitie s of p53-positive cells (P = 0.001, r(2) = 0.84). In the ICT, cells di splaying biotinylated DNA nicks were 3.8% +/- 2.7% of total cellularit y, while p53- and Bcl-2-positive cells represented 4.4% +/- 1.7% and 1 5.4% +/- 6.7% of total cells, respectively. It is suggested that p53 e xpression associated with DNA damage is a prevalent phenomenon in chro nically inflamed human gingiva, and that apoptosis may be a relevant p rocess for the maintenance of local immune homeostasis at sites of chr onic bacterial challenge in vivo.