One of the most interesting and biologically important functions of salivary glycoproteins is their ability to serve as bacterial receptors. Although microbial adhesion and/or clearance from the oral cavity is the result of a complex interplay of many factors, interactions between bacterial proteins (e.g., adhesin, lectins) and the carbohydrate portions of the salivary molecules are often an important component of the process. Structural work from the Fisher laboratory that was completed over the last decade resulted in the unexpected finding that individual salivary glycoproteins carry unique oligosaccharide structures. In addition, we demonstrated that these glycoprotein-specific carbohydrate sequences can direct either bacterial or neutrophil adherence to the molecules they modify. Together, these results suggest that the manner in which salivary proteins are glycosylated could be an important factor in determining oral health. Very recently we showed that saliva samples from 5 of our 67 saliva donors lack the epitope that promotes leukocyte adherence, sialyl Lex (sLex), but still express oligosaccharides that act as bacterial receptors. Mice and humans who lack the glycosyltransferase that encodes sLex have greatly impaired immune function. In this context, we propose that individuals with saliva that lacks the epitope have an increased risk of developing oral infections. As a first step toward testing this hypothesis, we will determine whether the sLex-phenotype is associated with the development of periodontitis and/or smooth surface caries. If this hypothesis proves correct, than our laboratory findings could lead to a test for predicting oral health, analogous to using IL-1 genotype as an indicator of susceptibility to severe periodontitis in adults.
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