Mast cells act as phagocytes against the periodontopathogen Aggregatibacter Actinomycetemcomitans

Background: Evidence to date shows that mast cells play a critical role in immune defenses against infectious agents, but there have been no reports about involvement of these cells in eliminating periodontopathogens. In this study, the phagocytic ability of mast cells against Aggregatibacter actinomycetemcomitans compared with macrophages is evaluated. Methods: In vitro phagocytic assays were conducted using murine mast cells and macrophages, incubated with A. actinomycetemcomitans, either opsonized or not, with different bacterial load ratios. After 1 hour, cells were stained with acridine orange and assessed by confocal laser-scanning electronmicroscopy. Results: Phagocytic ability of murine mast cells against A. actinomycetemcomitans was confirmed. In addition, the percentage of mast cells with internalized bacteria was higher in the absence of opsonization than in the presence of opsonization. Both cell types showed significant phagocytic activity against A. actinomycetemcomitans. However, the percentage of mast cells with non-opsonized bacteria was higher than that of macrophages with opsonized bacteria in one of the ratios (1:10). Conclusions: This is the first report about the participation of murine mast cells as phagocytes against A. actinomycetemcomitans, mainly in the absence of opsonization with human serum. Our results may indicate that mast cells act as professional phagocytes in the pathogenesis of biofilmassociated periodontal disease

Phenotypic and genotypic features of Aggregatibacter actinomycetemcomitans isolated from patients with periodontal disease

Aggregatibacter actinomycetemcomitans is strongly implicated in the pathogenesis of periodontitis. In this study, the phenotypic and genotypic features of A. actinomycetemcomitans and the presence of genes involved in toxicity were determined. Sixty-five patients with periodontal pocket and 48 healthy subjects were evaluated. Biotyping, adherence and invasion, neuraminidase and biofilm production, presence of capsule and fimbria, as well as the presence of flp-1, apaH, ltx, and cdt genes were determined. Biotype II was the most prevalent. Sixty-six strains were adherent and 33 of them were able to invade KB cells. Sixty strains produced neuraminidase, and 55 strains biofilms. Strains showed capsule but not fimbriae. Forty-six strains were cytotoxic, and most strains harbored the apaH and flp-1 genes. LTX promoter and the ltxA gene were observed in all strains from periodontal patients. The cdtA gene was observed in 50 (71.4%) strains, cdtB in 48 (68.6%) strains, cdtC in 60 (85.7%), and cdtABC in 40 (57.1%) strains. The presence of A. actinomycetemcomitans harboring the cdtC gene from healthy subjects may represent a transitory microorganism in the oral microbiota. More studies are necessary to understand the real role of this microorganism in the pathogenesis of periodontal disease

Altered phenotype and function of dendritic cells in individuals with chronic periodontitis

OBJECTIVE: To investigate the effects of periodontal bacterial lysates on maturation and function of mature monocyte-derived dendritic cells (m-MDDCs) derived from individuals with chronic periodontitis (CP) or healthy periodontal tissue (HP). DESIGN: m-MDDCs derived from peripheral blood monocytes, cultured for 7 days in presence of interleukin (IL)-4 and granulocyte-macrophage colony stimulating factor (GM-CSF), were stimulated with lysates of Streptococcus sanguinis, Prevotella intermedia, Porphyromonas gingivalis, or Treponema denticola on day 4, and were then phenotyped. IL-10, IL-12 and IFN-gamma concentration in the supernatant of cultures were measured. RESULTS: Expression of HLA-DR was lower in bacterial-unstimulated mature m-MDDC from CP compared to HP (p=0.04), while expression of CD1a and CD123 were higher in CP. The expression pattern of HLA-DR, CD11c, CD123, and CD1a did not change on bacterial stimulation, regardless of the bacteria. Stimulation with P. intermedia upregulated CD80 and CD86 in CP cells (p≤0.05). Production of IL-12p70 by bacterial-unstimulated m-MDDCs was 5.8-fold greater in CP compared to HP. Bacterial stimulation further increased IL-12p70 production while decreasing IL-10. Significantly more IFN-gamma was produced in co-cultures of CP m-MDDCs than with HP m-MDDCs when cells were stimulated with P. intermedia (p=0.009). CONCLUSIONS: Bacterial-unstimulated m-MDDC from CP exhibited a more immature phenotype but a cytokine profile biased towards proinflammatory response; this pattern was maintained/exacerbated after bacterial stimulation. P. intermedia upregulated co-stimulatory molecules and IFN-gamma expression in CP m-MDDC. These events might contribute to periodontitis pathogenesis