Polybacterial challenge effects on cytokine/chemokine production by macrophages and dendritic cells

To investigate the polymicrobial infection of periodontal disease, which elicits inflammatory mediators/cytokines/chemokines in the local gingival tissues, and a polybacterial challenge of antigen-presenting cells, e.g. macrophages and dendritic cells (DCs), at the mucosal surface.

The cytokine/chemokine profiles of human macrophages and DCs in response to polybacterial challenges were investigated.

Oral Gram-negative bacteria elicited significantly greater IL-8 levels from macrophages, compared to Gram-positive bacteria. Gram-positive bacteria did not show synergism in inducing this chemokine from macrophages. In contrast, pairs of oral Gram-negative bacteria elicited synergistic production of IL-8 by macrophages. Similar results were not observed with TNFα, which only appeared additive with the polybacterial challenge. Selected Gram-negative bacterial pairs synergized in IL-6 production by immature DCs. In mature DCs (mDCs), a Porphyromonas gingivalis/Fusobacterium nucleatum and Porphyromonas intermedia/F. nucleatum polybacterial challenge resulted in significant synergism for IL-6 and TNFα levels. However, only the Pi/Fn combination synergized for IL-12 production and there appeared to be no polybacterial effect on IL-10 production by the mDCs.

These results indicate that a polybacterial challenge of cells linking innate and adaptive immune responses results in varied response profiles that are dependent upon the characteristics of the microorganisms that are components of the polybacterial complex.