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Updated: Jul 24, 2026
Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Published on: August 9, 2011
Murine Lyme disease: no evidence for active immune down-regulation in resolving or subclinical infection
R R Montgomery1, X M Wang, S E Malawista
1Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520-8031, USA. ruth.montgomery@yale.edu
Abstract:
Macrophages in vitro rapidly ingest and kill Borrelia burgdorferi, yet some spirochetes in vivo may survive in the host and lead to complications of Lyme disease. One strategy for such survival may be the down-regulation of the immune system. To test this, we evaluated the degree of macrophage activation in a site of active disease-the heart-by examining cytokine expression in murine macrophages from control and B. burgdorferi-infected animals. Using double-label immunofluorescent staining in situ, we showed that infiltrating macrophages in infected hearts produce interleukin (IL)-1. By semiquantitative reverse transcription-polymerase chain reaction analysis, increased levels of mRNA were measured for the proinflammatory cytokines IL-1, tumor necrosis factor-alpha, and IL-12 during peak and resolving disease. No increases in the anti-inflammatory cytokines IL-10 and transforming growth factor-beta were detected. In an infected site without active disease--the peritoneal cavity--no increases in levels of proinflammatory or anti-inflammatory cytokines were detected in local macrophages. Thus, there is no evidence of pressure toward the down-regulation of inflammatory activity in the regions tested.
Insights
Macrophages combat Borrelia burgdorferi, but survival can cause Lyme disease complications. This study found no evidence of immune system down-regulation in infected mouse hearts, suggesting inflammation is not suppressed.
Area of Science:
- Immunology
- Microbiology
- Pathology
Background:
- Macrophages are crucial in fighting Borrelia burgdorferi (Lyme disease agent).
- Spirochete survival in vivo may involve immune system suppression.
- Understanding macrophage activation in Lyme disease is vital for treatment.
Purpose of the Study:
- To evaluate macrophage activation in active Lyme disease sites.
- To assess cytokine expression in murine macrophages during Borrelia burgdorferi infection.
- To determine if immune down-regulation occurs in infected host tissues.
Main Methods:
- Double-label immunofluorescent staining in situ for cytokine detection.
- Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) for mRNA analysis.
- Analysis of macrophages from infected murine hearts and peritoneal cavities.
Main Results:
- Infiltrating macrophages in infected hearts produced interleukin-1 (IL-1).
- Increased mRNA levels for pro-inflammatory cytokines (IL-1, TNF-α, IL-12) were observed in infected hearts.
- No increase in anti-inflammatory cytokines (IL-10, TGF-β) or cytokine changes in the peritoneal cavity were detected.
Conclusions:
- Macrophage activation with pro-inflammatory cytokine production occurs in infected heart tissue during Lyme disease.
- There is no evidence of immune down-regulation in the tested regions.
- Inflammatory activity is not suppressed in active Lyme disease sites studied.
