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Demyelination in the central nervous system following a delayed-type hypersensitivity response to bacillus

M K Matyszak1, V H Perry

  • 1University Department of Pharmacology, University of Oxford, U.K.

Neuroscience
|February 1, 1995
PubMed

Insights

Bacillus Calmette-Guérin (BCG) sequestered in the central nervous system (CNS) can trigger a delayed-type hypersensitivity response, causing bystander myelin damage. This immune response persists for months, highlighting a model for CNS autoimmunity.

Area of Science:

  • Neuroimmunology
  • Central Nervous System (CNS) Autoimmunity
  • Delayed-Type Hypersensitivity (DTH)

Background:

  • Investigating immune responses within the CNS is crucial for understanding neuroinflammatory diseases.
  • The blood-brain barrier typically restricts immune cell entry, but certain conditions can breach this defense.
  • Models are needed to study CNS-specific immune reactions and their consequences, such as demyelination.

Purpose of the Study:

  • To establish and characterize a novel model of delayed-type hypersensitivity (DTH) in the CNS.
  • To investigate the CNS immune response to an antigen (Bacillus Calmette-Guérin) sequestered behind the blood-brain barrier.
  • To determine if this CNS immune response leads to bystander damage, specifically myelin damage.

Main Methods:

  • Intracranial injection of heat-killed Bacillus Calmette-Guérin (BCG) in rats.
  • Subsequent subcutaneous immunization with BCG in complete Freund's adjuvant to induce peripheral sensitization.
  • Monitoring of inflammatory cell infiltration (myelomonocytic response) via histology and immunohistochemistry.
  • Assessment of blood-brain barrier integrity by detecting serum protein extravasation.
  • Detection of BCG debris and myelin basic protein damage using specific antisera.

Main Results:

  • A single intracranial BCG injection induced a transient myelomonocytic response in the CNS.
  • BCG debris persisted in the CNS despite the initial inflammatory response, indicating incomplete clearance.
  • Peripheral sensitization led to a robust DTH response at the BCG deposit site, characterized by mononuclear phagocytes and T cells.
  • Significant bystander myelin damage was observed in the affected CNS regions (dorsal hippocampus).
  • The DTH response and associated pathology were sustained for at least five months post-peripheral immunization.

Conclusions:

  • A CNS DTH model can be established using sequestered BCG, leading to significant immune-mediated pathology.
  • The model demonstrates that CNS-localized antigens, even when initially contained, can elicit a potent and damaging autoimmune response upon peripheral sensitization.
  • This study provides a valuable platform for investigating mechanisms of CNS autoimmunity and potential therapeutic targets for demyelinating diseases.

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