Bacterial antibody titers in ligature-induced periodontitis in beagle dogs.

Serum antibodies to indigenous bacteria in ten beagle dogs were examined over a 7-month period during the development of ligature-induced periodontitis. Gram-negative strains comprised approximately 75% of the cultivable periodontitis microflora with a predominance of black-pigmented Bacteroides species. A total of 44 bacterial strains representing the predominant cultivable subgingival beagle dog microflora was selected for antibody determination. The IgG and, in some cases, IgM serum antibody titers to these organisms were determined by indirect immunofluorescence. The antibody titers to most test strains remained unchanged during the experimental period. Gram-negative bacteria generally exhibited lower titers than the Gram-positive bacteria. Especially low titers were found for the black-pigmented Bacteroides. Four dogs that developed the most severe periodontitis showed about 2-fold higher IgG titers to some Gram-negative anaerobic rods in the pre-ligation period than dogs that developed a more moderate periodontitis. These data suggested a possible diagnostic value of such antibody determinations. However, the overall finding of the present study was that serum antibody titers to key periodontopathic organisms remained low throughout the experiment. This result may suggest that the rapid periodontal destruction in ligature-induced periodontitis is due in part to an inadequate antibody response against the infecting microorganisms and their pathogenic products.