Localized expression of mRNA for phagocyte-specific chemotactic cytokines in human periodontal infections
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M S Tonetti1, M A Imboden, L Gerber
1Department of Peridontology and Fixed Prosthodontics, School of Dental Medicine, University of Bern, Switzerland.
Abstract:
In bacterial infections, mononuclear and polymorphonuclear phagocytes are key components of host defenses. Recent investigations have indicated that chemokines are able to recruit and activate phagocytes. In particular, interleukin-8 (IL-8) attracts polymorphonuclear leukocytes (PMNs), while monocyte chemoattractant protein-1 (MCP-1) is selective for cells of the monocyte/macrophage lineage. In this investigation, we analyzed the in situ expression of IL-8 and MCP-1 mRNAs in human periodontal infections. Specific mRNA was detected by in situ hybridization using 35S-labeled riboprobes in frozen tissue sections. Phagocytes (PMNs and macrophages) were specifically detected as elastase-positive or CD68+ cells by a three-stage immunoperoxidase technique. Results indicated that expression of phagocyte-specific cytokines was confined to selected tissue locations and, in general, paralleled phagocyte infiltration. In particular, IL-8 expression was maximal in the junctional epithelium adjacent to the infecting microorganisms; PMN infiltration was more prominent in the same area. MCP-1 was expressed in the chronic inflammatory infiltrate and along the basal layer of the oral epithelium. Cells of the monocyte/macrophage lineage were demonstrated to be present in the same areas. The observed expression pattern may be the most economic way to establish a cell-type-selective chemotactic gradient within the tissue that is able to effectively direct polymorphonuclear phagocyte migration toward the infecting microorganisms and modulate mononuclear phagocyte infiltration in the surrounding tissues. This process may optimize host defenses and contribute to containing leukocyte infiltration to the infected and inflamed area, thus limiting tissue damage.
Insights
Interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) guide immune cells in periodontal infections. Their expression patterns optimize host defenses by directing phagocytes to infection sites, minimizing tissue damage.
Area of Science:
- Immunology
- Oral Biology
- Pathology
Background:
- Phagocytes, including mononuclear and polymorphonuclear cells, are crucial for combating bacterial infections.
- Chemokines like interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) are known to recruit and activate these phagocytes.
- IL-8 specifically attracts polymorphonuclear leukocytes (PMNs), while MCP-1 targets monocytes/macrophages.
Purpose of the Study:
- To investigate the in situ expression of IL-8 and MCP-1 mRNAs in human periodontal infections.
- To correlate the expression patterns of these chemokines with the infiltration of specific phagocyte types.
Main Methods:
- In situ hybridization was used to detect IL-8 and MCP-1 mRNAs in frozen tissue sections.
- Immunoperoxidase staining identified elastase-positive cells (PMNs) and CD68+ cells (monocytes/macrophages).
Main Results:
- Chemokine expression was localized and generally corresponded with phagocyte infiltration patterns.
- IL-8 expression peaked in the junctional epithelium near microorganisms, correlating with PMN presence.
- MCP-1 was found in chronic inflammatory infiltrates and the oral epithelium's basal layer, alongside monocytes/macrophages.
Conclusions:
- The localized expression of IL-8 and MCP-1 creates selective chemotactic gradients within periodontal tissues.
- This targeted recruitment optimizes host defense by directing PMNs to pathogens and modulating monocyte infiltration.
- This mechanism enhances host defense and limits tissue damage by containing leukocyte infiltration to inflamed areas.