Immunofluorescent localization of soluble dental plaque components in human gingiva affected by periodontitis

In order to determine if soluble plaque antigens are found in the gingiva in the course of periodontal disease, plaque was collected from 16 subjects with periodontitis, an extarct of the plaque was prepared, and antisera to the extarct were induced in rabbits; the sera were conjugated with fluorescein isothiocyanate and used in direct immunofluorescent staining of gingival biopsies from the same subjects. Fluorescent staining suggestive of soluble plaque substances were found in all biopsies, most commonly intracellularly in mononuclear cells of the connective tissue. The most common locations of the cells were subjacent to sulcular epithelium, deeper in the connective tissue in chronic inflammatory infiltrates or near vessels, or close to the oral epithelium. Occasionally a fluorescent cell could be seen within a vessel lumen. These localizations possibly represent engulfed materials within macrophages. Other morphologic appearances of fluorescence were seen that might represent immune complexes. The number of fluorescent sites varied among the subjects and seem to be related to the degree of clinical inflammation. Similar results were found using biopsies from subjects who did not contribute plaque for preparing antisera, indicating that the plaque constituents were not specific to an individual.