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Immunostimulatory CpG-DNA activates murine microglia.
Alexander H Dalpke1, Martin K-H Schäfer, Markus Frey
1Institute of Medical Microbiology and Hygiene, Department of Molecular Neuroscience, Philipps-University Marburg, Baldinger Strasse, 35033 Marburg, Germany.
Journal of Immunology (Baltimore, Md. : 1950)
|May 8, 2002
Summary
Bacterial DNA with CpG motifs activates immune cells, including microglia in the central nervous system (CNS). This CpG-DNA stimulation enhances microglial immune responses and may contribute to CNS inflammation and Th1-type immune reactions.
Area of Science:
- Immunology
- Neuroscience
- Microbiology
Background:
- Unmethylated CpG dinucleotides (CpG-DNA) in bacterial DNA activate innate immune cells via Toll-like receptor 9 (TLR-9).
- CpG-DNA is a potent immunostimulant, inducing inflammation and acting as a Th1-polarizing agent, making it a potential vaccine adjuvant.
- The role of CpG-DNA in central nervous system (CNS) immune responses, particularly involving microglial cells, requires further investigation.
Purpose of the Study:
- To investigate the effects of CpG-DNA on microglial cells, the primary immune cells of the CNS.
- To determine if microglia express TLR-9 and respond to CpG-DNA stimulation in vitro and in vivo.
Main Methods:
- Analysis of TLR-9 mRNA expression in primary microglial cells and microglial cell lines.
- In vitro stimulation of microglial cells with CpG-DNA and assessment of cytokine (TNF-alpha, IL-12) and nitric oxide (NO) production.
- Evaluation of cell surface molecule (MHC class II, B7-1, B7-2, CD40) upregulation and phagocytic activity.
- In vivo studies involving intracerebroventricular injection of CpG-DNA and analysis of microglial activation and gene expression using in situ hybridization.
Main Results:
- Microglial cells express TLR-9 mRNA and are activated by CpG-DNA in vitro, leading to the induction of TNF-alpha, IL-12p40, IL-12p70, and NO.
- CpG-DNA stimulation upregulates key immune molecules (MHC class II, B7-1, B7-2, CD40) and enhances microglial phagocytic activity.
- In vivo administration of CpG-DNA activates microglial cells in the CNS, inducing TNF-alpha and IL-12p40 transcripts.
Conclusions:
- Microglia are sensitive to bacterial CpG-DNA, indicating a significant role for this molecule in CNS immune responses.
- CpG-DNA may contribute to the pathogenesis of CNS infections by activating microglia and promoting Th1-dominated immune reactions.
- These findings highlight the potential involvement of bacterial DNA in triggering and sustaining inflammatory processes within the CNS.