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Immune system response in Alzheimer's disease
P L McGeer1, H Akiyama, S Itagaki
1Kinsmen Laboratory of Neurological Research, Department of Psychiatry, University of B.C., Vancouver.
Summary
The immune system, specifically the classical complement pathway and reactive microglia, is involved in Alzheimer's disease pathogenesis. Alzheimer's brain tissue shows complement protein attachment and immune cell activation.
Area of Science:
- Neuroimmunology
- Pathology of Alzheimer's Disease
- Complement System Biology
Background:
- The immune system plays a role in Alzheimer's disease (AD) pathogenesis.
- Evidence includes complement protein deposition and immune cell activation in AD brain tissue.
Purpose of the Study:
- To investigate the involvement of the classical and alternative complement pathways in AD.
- To evaluate the cellular immune response, including microglia and T-cells, in AD.
Main Methods:
- Immunohistochemical staining of post-mortem Alzheimer's brain tissue.
- Antibodies targeting complement pathway components (classical and alternative).
- Antibodies for immune cell markers (microglia, T-cells, astrocytes, endothelial cells).
Main Results:
- Classical complement pathway components (C1q, C3d, C4d, C5b-9) were detected in AD brain tissue, localizing to plaques, neurites, and neurons.
- The alternative complement pathway was not detected.
- Reactive microglia expressing HLA-DR and T-cells (CD4+, CD8+) were identified in diseased brain tissue.
- Astrocytes did not express MHC antigens, while endothelial cells expressed MHC class I, and microglia/leukocytes expressed MHC class II.
Conclusions:
- The classical complement pathway is activated in Alzheimer's disease.
- Cellular immune responses involving reactive microglia and T-cells are present in AD.
- These findings highlight the immune system's significant role in AD pathology.