NEUTROPHIL MIGRATION INTO THE GINGIVAL SULCUS IS ASSOCIATED WITH TRANSEPITHELIAL GRADIENTS OF INTERLEUKIN-8 AND ICAM-1

THE EXPRESSION OF ADHESION MOLECULES and the local production of chemo tactic cytokines within the epithelium are considered to be key events in neutrophil (PMN) migration at sites of mucosal infections. In thei r journey toward the gingival sulcus, PMNs have been shown to selectiv ely migrate through the junctional epithelium. Little, however, is kno wn about the molecular mechanisms involved in this key process aimed a t the control of subgingival bacterial plaque. This investigation desc ribes the expression of IL-8 mRNA-positive cells and the establishment of a gradient of intercellular adhesion molecule-1 (ICAM-1) receptors within the junctional epithelium of clinically healthy gingiva. Expre ssion of ICAM-1 and IL-8 was topographically associated with the area of PMN migration; i.e., the junctional epithelium. Levels of ICAM-1 ex pression increased from the basal cells toward the surface of the junc tional epithelium and thus toward areas exposed to bacterial challenge s. IL-8 mRNA-positive cells were also present at highest density in th e most superficial junctional epithelial layers. The combination of th e haptotactic stimuli, resulting from the interaction of the PMN's bet a 2 integrin receptors with the gradient of ICAM-1 expression, and the location of IL-8 mRNA-positive cells, consistent with the establishme nt of a discrete PMN chemotactic source, may play an important physiol ogic role in efficiently routing PMNs to the gingival sulcus. This pro cess contributes to the maintenance of a local host-parasite equilibri um and to the limitation of PMN-associated tissue damage.