BACKGROUND: It has been suggested that hyper-responsiveness of monocytes to the products of dental plaque, especially the endotoxin of Gram-negative bacteria and the secretion of high levels of pro-inflammatory cytokines, may have a role in the pathogenesis of aggressive periodontitis (AP). To investigate this possibility, IL-6 production by cultured peripheral blood monocytes before and after stimulation by E. coli lipopolysaccharide (LPS) in AP patients was evaluated. MATERIAL/METHODS: Fifteen patients with AP were compared with 15 periodontally healthy controls in a case control study. Monocytes were obtained from peripheral blood samples and cultured. The reaction of monocytes was studied by their IL-6 production using ELISA before and six hours after stimulation by 0.1 microg/ml E. col. LPS. The Wilcoxon and Mann-Whitney U tests were used to compare the groups. RESULTS: There was no significant difference in IL-6 production levels before LPS stimulation between patients and controls. Upon LPS stimulation, IL-6 levels increased in both the patient and control groups compared with their IL-6 levels before stimulation. IL-6 production after LPS stimulation in the patients was higher than controls, but this was not statistically significant. However, the increase in IL-6 production as a result of LPS stimulation was significantly higher in patients than in controls. CONCLUSIONS: Increased monocyte responsiveness may play a potential role in the pathogenesis of AP. However, whether this is an intrinsic characteristic of the monocyte/macrophage cells of AP patients or just a priming effect as a result of the periodontal disease remains to be investigated.

Keywords: Escherichia coli, Case-Control Studies, Interleukin-6 - metabolism, Iran, Lipopolysaccharides - toxicity, Monocytes - immunology, Periodontitis - immunology