Monocyte Activation by Porphyromonas gingivalis LPS in Aggressive Periodontitis using Whole Blood Culture

Host immune response to bacterial plaque pathogens play a crucial role in determining the outcome and severity of periodontal disease. Hyper-responsiveness of monocytes to bacterial LPS have been hypothesized to be associated with the severity of periodontal disease. Particularly, high level production of monocytic secretory mediators such as PGE2 in susceptible periodontitis subjects have been reported. Objectives: In this study, we used whole blood assays to compare monocyte activation after stimulating with LPS from periodontopathic bacteria, Porphyromonas< gingivalis between aggressive periodontitis patients and healthy periodontal subjects. Methods: Heparinized blood were obtained from 17 pairs of the aggressive periodontitis patients who were in a maintenance care and healthy sujects (age and sex matched). Upon stimulation with varying doses fo highly purified P. gingivalis LPS (1,3,10 ng/ml), expression of co-stimulatory molecules on monocytes were analysed by flow cytometry and production of inflammatory mediators were monitored by ELISA. In addition, expression of CD69, early activation marker, on NK and gd T cells were evaluated. Results: LPS stimulation resulted in a dose dependent up-regulation of co-stimulatory molecules, CD40, CD80 and CD86, on monocytes, and up-regulation of CD69 on NK and gd T cells in both the patient and healthy control groups. Generally, aggressive periodontitis patients seem to show lower expression of these molecules than healthy controls at any tested LPS concentrations but the significant difference (P<0.05) were found in CD80 expression on monocytes (all LPS concentrations) and CD69 expression on NK cells (10 ng/ml). Production of PGE2 and IL-1b in P. gingivalis LPS stimulated whole blood cultures was quite similar between the two groups. Conclusions: By using the whole blood assay which probably represent the better physiological condition, we did not observe hyper-responsiveness of monocytes to bacterial challenge in aggressive periodontitis. (supported by Thailand Research Fund, RDG3/05/2543)