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 the magnitude of host antibody response and periodontal disease status. Previous studies also reported that Porphyromonas gingivalis-specific IgG subclass antibodies were elevated in sera from adult periodontitis patients. However, the role and the association of these IgG subclass antibodies to the development 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 untreated periodontitis patients. Methods: Serum samples were taken from 20 treated and maintained periodontitis patients (SPT patients), 30 untreated patients and 19 periodontally healthy subjects. We determined the IgG subclass antibody titers to P. gingivalis whole cells using an enzyme-linked immunosorbent assay (ELISA). Subgingival plaque samples were taken from the mesio-buccal surface of 6 randomly selected teeth of SPT patients and evaluated for the presence of P. gingivalis by immunofluorescence microscopy. Clinical measurements were also taken including full mouth intraoral radiographs to measure interproximal alveolar bone loss at baseline (BLSI) and at a 5-year recall visit in the SPT patients (BLS2). Results: Our results indicated that both patient groups had detectable levels of IgG1, IgG2, and IgG4. Significantly higher IgG1 was observed in both patient groups compared to the healthy subjects. The untreated patients also exhibited significantly elevated IgG2 response (p <0.05). The mean IgG4 level of the SPT patients was significantly higher compared to the other subject group (p <0.05). A statistically significant positive correlation between IgG2 levels and changes in bone levels (ABLS: BLS2-BLS1) was seen in the 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), although the mean prevalence of P. gingivalis in the 2 groups did not differ significantly. Conclusion: Our data suggest that the prolonged IgG2 response after periodontal treatment may be indicative of recurrent or persistent periodontal destruction.