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The aim of this study was to investigate the nature of a factor present in human whole saliva which causes the aggregation of certain oral bacteria. It seemed possible that the factor causing aggregation could play a part in plaque formation in that it could promote adhesion of organisms to the teeth and contribute to the mutual adhesion of the organisms in the plaque. Agarose column chromatography of human whole saliva gave a void volume peak which contained the aggregating activity. Investigation of this material showed it to contain 33% protein, 19% anthrone positive carbohydrate, 2.9% N-acetyl neuraminic acid and substantial amounts of hexosamine. Data from ultracentrifugal analysis, agarose column chromatography, amino acid analysis, isoelectric focusing and cetyl trimethylammonium bromide fractionation indicated that the active material was a high molecular weight glycoprotein which exists in solution in a random coil configuration. It was further found that the active material was selectively adsorbed on to the hydroxy-apatite surface and also that a component with properties similar to those described above could be isolated from dental plaque. It seems, therefore, that there is, in whole saliva, a high molecular weight glycoprotein, which selectively adsorbs on to the apatite surface and which causes aggregation of certain oral organisms. It seems possible that this component plays a significant role in the initial selective adhesion of certain oral organisms to the tooth surface, as well as being involved in the mutual adhesion of the organisms in the developing plaque.
Hay et al. (Fri,) studied this question.