Salivary IgA Antibody Responses to Oral Bacteria in Down's Syndrome

Down's Syndrome (DS) is associated with numerous functional disorders, high rates of infections, malignancies, and autoimmune diseases, which may be linked to abnormalities of the immune system, including altered immunoglobulin and antibody production. As such, defective humoral mucosal immune responses have been suggested to contribute to increased oral disease in DS subjects. Objective: To determine the characteristics of salivary responses to an array of oral pathogens in DS patients related to clinical presentation of periodontal disease. Methods: 33 DS patients (9-27 yo) and 28 normal subjects (NS, 7-18 yo) were evaluated for periodontal disease measures and salivary IgA antibody to 8 bacteria (A. actinomycetemcomitans, F. nucleatum, P. gingivalis, P. nigrescens, E. corrodens, M. micros, P. intermedia, E. nodatum) using ELISA. Results: IgA antibody to bacteria associated with subgingival plaque was increased 2-4 fold in the DS patients compared to the NS. These differences were significant (p<0.0001) for all bacteria except Ec, when adjusted for multiple comparisons. IgA relationships to clinical parameters of periodontal health/disease in the DS vs. NS provided a very different profile. Generally, IgA levels were not correlated with any clinical parameter in the DS patients. In contrast, in the NS group, IgA to 8/9 bacteria were negatively correlated (p<0.05) with a combined oral hygiene index and antibody levels to Ec and Pi were also negatively correlated with the calculus index. Conclusions: The results identify a unique profile of salivary IgA antibody to periodontal disease associated bacteria in Down's Syndrome compared to normal subjects. IgA antibody was unrelated to age in either group; however, in NS it appeared that the IgA antibody may positively impact periodontal health, while in DS patients it appears to be an ineffective response related to the clinical presentation. Supported by National Research Center of Egypt and the University of Kentucky.