Studies on human dental plaque. 2. Immunochemical characteristics

From collected supragingival plaque, extracts were prepared for immunochemical analyses. Extracted sediments were examined by fluorescein-labeled antibodies for the presence of immunoglobulins. Precipitation with monospecific and polyvalent antisera revealed IgA, IgG, secretory component, C3, alpha2macroglobulin, lactoferrin, and albumin in the extracts. Gel filtration of pooled plaque extract yielded two fractions that contained the aforementioned proteins and a prominent, dialyzable third fraction that was immunochemically nonreactive. IgA, IgG, secretory component, and light chains were shown, by immunofluorescence, to be present in washed, pooled plaque sediment. Release of these immunoglobulins by urea treatment indicated their probable participation in immune complexes.