MOLECULAR FACTORS ASSOCIATED WITH COMPARTMENTALIZATION OF GINGIVAL IMMUNE-RESPONSES AND TRANSEPITHELIAL NEUTROPHIL MIGRATION

PMN migration into the gingival sulcus is a lightly regulated process aimed at selectively increasing leukocyte availability at the site of bacterial plaque aggression, i.e. the superficial portion of the junct ional epithelium. The evidence reviewed iu this paper indicates that, besides the action of complement fragments, arachidonic acid metabolit es, formyl peptides and other bacterial products, the establishment of a gradient of ICAM-1 expression across the junctional epithelium and the expression of IL-8 in its superficial layers probably represent im portant regulatory mechanisms leading to PMN migration into the gingiv al sulcus. Such mechanisms can be regulated by the autocrine and parac rine action of some pro-inflammatory cytokines and could possibly be i nitiated by specific bacteria-keratinocyte interactions. The advantage of such a redundant regulatory mechanism leading to PMN transepitheli al migration is probably related to the key role of the neutrophiI in the maintenance of a local host-parasite equilibrium on one side, and on the tissue injury associated with PMN persistence or random migrati on within periodontal tissues on the other. Several investigations are in progress aimed at identifying the initial environmental stimuli le ading to PMN recruitment into the gingival sulcus and at Further explo ring the important regulatory events.