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Published on: March 1, 2011
Effect of oral bacteria on peripheral blood leukocyte interleukin-6 and soluble interleukin-6 receptor production
R A Lindemann1, S A Kinder Haake, M Kjeldsen
1Section of Oral Biology, UCLA School of Dentistry 90095-1668, USA.
Abstract:
To determine the effect of pathogenic oral bacteria on interleukin 6 (IL-6) and soluble IL-6 receptor production, we measured their release by human peripheral blood mononuclear cells in vitro. Unseparated peripheral blood mononuclear cells, peripheral blood lymphocytes (monocyte depleted), pure T cells, or monocytes were cultured with Actinobacillus actinomycetemcomitans, Capnocytophaga gingivalis, Capnocytophaga ochracea, Fusobacterium nucleatum or Porphyromonas gingivalis for 24 h. Supernatants were tested for IL-6 and soluble IL-6 receptor by enzyme-linked immunosorbent assay. Only monocytes and peripheral blood mononuclear cells responded with significant IL-6 release in the presence of all bacteria tested. However, peripheral blood lymphocytes were capable of producing IL-6 when activated by phytohemagglutinin or IL-2 followed by bacteria, though substantially less than cultures containing monocytes. No bacteria tested increased soluble IL-6 receptor release over spontaneous soluble IL-6 receptor release. We conclude that monocytes release IL-6 after contact with oral pathogens; however, soluble IL-6 receptor from T cells and monocytes is constitutively produced and may modulate IL-6 actions.
Insights
Monocytes release interleukin 6 (IL-6) when exposed to oral pathogens. Soluble IL-6 receptor is constitutively produced by immune cells and may regulate IL-6 activity.
Area of Science:
- Immunology
- Oral Microbiology
- Cell Biology
Background:
- Interleukin 6 (IL-6) is a key cytokine in inflammation.
- Soluble IL-6 receptor (sIL-6R) modulates IL-6 activity.
- Oral pathogenic bacteria are implicated in various inflammatory conditions.
Purpose of the Study:
- To investigate the impact of specific oral pathogenic bacteria on IL-6 and sIL-6R production by human peripheral blood mononuclear cells (PBMCs).
- To identify which immune cell subsets within PBMCs are responsible for IL-6 and sIL-6R release upon bacterial stimulation.
Main Methods:
- Human PBMCs, lymphocytes, T cells, and monocytes were cultured with five oral bacteria: Actinobacillus actinomycetemcomitans, Capnocytophaga gingivalis, Capnocytophaga ochracea, Fusobacterium nucleatum, and Porphyromonas gingivalis.
- Supernatants were analyzed for IL-6 and sIL-6R concentrations using enzyme-linked immunosorbent assay (ELISA).
- Cellular responses were assessed after 24-hour incubation periods.
Main Results:
- Monocytes and PBMCs demonstrated significant IL-6 release when co-cultured with all tested oral bacteria.
- IL-6 production by peripheral blood lymphocytes was significantly lower compared to monocyte-containing cultures, even with activation.
- None of the tested oral bacteria elevated soluble IL-6 receptor release above baseline levels.
Conclusions:
- Monocytes are the primary responders to oral pathogens, releasing IL-6.
- Soluble IL-6 receptor is constitutively produced by T cells and monocytes.
- The constitutive production of sIL-6R suggests a role in modulating IL-6 signaling pathways in response to oral bacteria.
