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Murine macrophage interleukin-1 release by capsularlike serotype-specific polysaccharide antigens of Actinobacillus
T Takahashi1, T Nishihara, Y Ishihara
1Department of Dental Research, National Institute of Health, Tokyo, Japan.
Abstract:
Serotype-specific polysaccharide antigens (SPAs) were extracted from whole cells of Actinobacillus actinomycetemcomitans ATCC 29523 (serotype a), Y4 (serotype b), and NCTC 9710 (serotype c) by autoclaving and purified by chromatography on DEAE-Sephadex A-25 and Sephacryl S-300 columns. Y4 SPA induced interleukin-1 (IL-1) release by P388D1 murine macrophages. Polymyxin B had virtually no effect on the release of IL-1. Rabbit anti-murine IL-1 serum strongly suppressed the proliferation of C3H/HeJ mouse thymocytes induced with the culture supernatants of Y4 SPA-stimulated P388D1 cells and a submitogenic dose of concanavalin A. Gel filtration of the culture supernatants of Y4 SPA-stimulated macrophages on Sephacryl S-200 showed that an IL-1 peak at a point corresponding to approximately 16.5 kDa was eluted. The ability of SPAs from strains ATCC 29523 and NCTC 9710 to induce the release of IL-1 was lower than that of Y4 SPA. The IL-1-releasing ability of serotype a and c antigens was enhanced by deacetylation of both polysaccharides, suggesting that acetyl groups of these antigens might hinder the interaction between the antigens and macrophages.
Insights
Serotype-specific polysaccharide antigens from Actinobacillus actinomycetemcomitans stimulate interleukin-1 release in macrophages. Deacetylation enhanced this immune response, suggesting acetyl groups may inhibit antigen-macrophage interaction.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- Actinobacillus actinomycetemcomitans is associated with periodontal disease.
- Polysaccharide antigens (SPAs) are key components of bacterial cell walls.
- Interleukin-1 (IL-1) is a crucial cytokine in immune responses.
Purpose of the Study:
- To investigate the immunomodulatory effects of Actinobacillus actinomycetemcomitans serotype-specific polysaccharide antigens (SPAs).
- To determine the role of SPAs in inducing interleukin-1 (IL-1) release from macrophages.
- To explore the influence of polysaccharide structure, specifically acetylation, on immune cell activation.
Main Methods:
- Extraction and purification of SPAs from Actinobacillus actinomycetemcomitans serotypes a, b, and c using autoclaving and chromatographic techniques.
- Assay of IL-1 release from P388D1 murine macrophages stimulated with SPAs.
- Analysis of IL-1 activity using anti-murine IL-1 serum and concanavalin A.
- Gel filtration chromatography (Sephacryl S-200) to determine the molecular weight of released IL-1.
Main Results:
- Y4 SPA (serotype b) potently induced IL-1 release from P388D1 macrophages, with minimal inhibition by Polymyxin B.
- IL-1 release was confirmed by its ability to stimulate thymocyte proliferation, which was suppressed by anti-IL-1 serum.
- A peak corresponding to approximately 16.5 kDa was identified as IL-1.
- SPAs from serotypes a and c showed lower IL-1 inducing capacity, which was enhanced upon deacetylation, indicating steric hindrance by acetyl groups.
Conclusions:
- Actinobacillus actinomycetemcomitans SPAs, particularly serotype b, are potent inducers of macrophage-derived IL-1.
- Deacetylation of serotype a and c SPAs significantly enhances their IL-1 releasing capability.
- Acetylation of bacterial polysaccharide antigens may act as a mechanism to modulate or reduce host immune cell activation.