Levels of salivary IgA antibodies reactive with bacteria from dental plaque are associated with susceptibility to experimental gingivitis.

Serum IgG, IgA and IgM and salivary IgA antibody levels reactive with extracts from Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Eubacterium saburreum and Streptococcus mutans, were measured by enzyme-linked immunosorbent assay in samples from 12 persons before, during and after experimental gingivitis. The participants refrained from cleaning their teeth until 50% of their gingival units showed bleeding after gentle probing, but not longer than 15 days. Samples were taken from serum and saliva, before and during the period of experimental gingivitis, and up to 8 weeks after the start of the experiment. A pattern with minor fluctuations in specific serum and salivary antibody activities was consistently found in all patients. This indicates that immunoregulatory mechanisms succeed in maintaining unchanged antibody levels when plaque load increases. A subgroup of participants with low mean numbers of bleeding gingival units after plaque accumulation, showed significantly higher salivary IgA antibody levels reactive with S. mutans, A. actinomycetemcomitans and E. saburreum, as compared with the subgroup reaching high bleeding after probing scores (p < 0.05). When 1 person with outlying values (p < 0.05) for P. gingivalis was excluded from the tests, the former group also showed statistically significant higher salivary antibody levels to this bacterial species. High levels of salivary IgA directed against bacteria in dental plaque might thus protect against the development of gingivitis.