Induction of B Cells With a Regulatory Cytokine Profile by the Periodontal Pathogen Prevotella Intermedia

Objectives: Periodontitis is an inflammatory disease caused by biofilm-forming oral bacteria. B cells are the dominating immune cells in the periodontal lesion, but their role in periodontitis is obscure. We examined B-cell cytokine responses against two periodontal pathogens, Porphyromonas gingivalis and Prevotella intermedia.
Methods: Mononuclear cells from healthy donors were incubated with or without live bacteria for 15 hours, or with the polyclonal B-cell activator PMA-ionomycin for 4 hours. Subsequently, staining for CD19+ B cells and intracellular IL-10, TGF-β, IL-35, IL-6, and TNF- α was performed using appropriate antibodies, followed by flow cytometry.
Results: P. intermedia induced significant proportions of B cells producing the regulatory cytokines IL-10, TGF- β and IL-35 by B cells. The proportions of B cells producing pro-inflammatory cytokines such as IL-6 and TNF-α were not affected significantly by exposure to P. intermedia. P. gingivalis induced considerably lower numbers of cytokine-producing B cells than P. intermedia.
Conclusions: These in vitro findings suggest that P. intermedia induces a regulatory B-cell profile, which may suppress the immune system’s attack on periodontal bacterial biofilm.