Porphyromonas gingivalis - Specific IgG subclass antibody levels as immunological risk indicators of periodontal bone loss

Background: It has been well demonstrated a positive association between th e magnitude of host antibody response and periodontal disease status. Previ ous studies also reported that Porphyromonas gingivalis-specific IgG subcla ss antibodies were elevated in sera from adult periodontitis patients. Howe ver, the role and the association of these IgG subclass antibodies to the d evelopment of periodontal diseases are poorly understood. Aim: The aim of present investigation was to examine the relation of serum IgG subclass antibody levels and alveolar bone loss in treated and untreate d periodontitis patients. Methods: Serum samples were taken from 20 treated and maintained periodonti tis patients (SPT patients), 30 untreated patients and 19 periodontally hea lthy subjects. We determined the IgG subclass antibody titers to P. gingiva lis whole cells using an enzyme-linked immunosorbent assay (ELISA). Subging ival plaque samples were taken from the mesio-buccal surface of 6 randomly selected teeth of SPT patients and evaluated for the presence of P. gingiva lis by immunofluorescence microscopy. Clinical measurements were also taken including full mouth intraoral radiographs to measure interproximal alveol ar bone loss at baseline (BLSI) and at a 5-year recall visit in the SPT pat ients (BLS2). Results: Our results indicated that both patient groups had detectable leve ls of IgG1, IgG2, and IgG4. Significantly higher IgG1 was observed in both patient groups compared to the healthy subjects. The untreated patients als o exhibited significantly elevated IgG2 response (p <0.05). The mean IgG4 l evel of the SPT patients was significantly higher compared to the other sub ject group (p <0.05). A statistically significant positive correlation betw een IgG2 levels and changes in bone levels (ABLS: BLS2-BLS1) was seen in th e SPT patients (p <0.001). SPT patients with high IgG2 and low IgG4 showed greater bone loss than those with low IgG2 and high IgG4 (p <0.05), althoug h the mean prevalence of P. gingivalis in the 2 groups did not differ signi ficantly. Conclusion: Our data suggest that the prolonged IgG2 response after periodo ntal treatment may be indicative of recurrent or persistent periodontal des truction.