Induction of periodontal bone loss in athymic (nude) rats monoinfected with streptococcus mutans

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Abstract
In order to investigate the rule of the thymus‐dependent immune system in the development of marginal periodontitis, an experiment was performed on athymic (nude) and normal rats. Seven homozygous nude (mutual) Lewis rats and six heterozygous (rnu+) littermates with normal thymus function were monoinfected with Streptococcus mutans 6715. Six germfree nudes and six germfree heterozygoles at same age served as controls. The animals were killed after 90 days.Periodontal bone support on lower molars was registered blindly from magnified radiographs of rat heads. Serum antibody against S. mutans was detected indirect Immunofluorescence. Splentc T‐lymphocyte subpopulations were quantified in a fluorescence activated cell‐setter. Periodontal bone support was significantly diminished in both types of monoinfected rats irrespective of thymus function. Scrum antibody titer to S. mutans was increased equally in both monoinfected groups. Nude rats had significantly less mature T‐lymphocytes than rats with normal thymus and this parameter was not changed by monoinfection.The induction of periodontal destruction m an immune system is not necessary for development of periodontal discase in this model. The high titers of specific annbody to S. mutans seen in affected animals suggest that T‐independent immune reactions could be involved.