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Characterization and distribution of phagocytic macrophages in multiple sclerosis plaques
1Multiple Sclerosis Society Laboratory, Institute of Neurology, London, UK.
Abstract:
Populations of phagocytic cells in multiple sclerosis (MS) plaques were examined by quantitative immunocytochemical analysis of macrophage markers and myelin degradation products in serial cryostat sections from 10 cases of MS. Around lesions with ongoing demyelination expression of the Class II antigen HLA-DQ appeared to be a marker of microglial activation. Alpha 1-antichymotrypsin+ monocytes and myelin-laden macrophages expressing the later differentiation markers Ber-MAC3 and RFD7 were predominantly perivascular in location. On the basis of the distribution of oil red O (ORO)+ phagocytes and myelin loss, plaques were divided into groups representing different stages in lesion development. In early lesions (group 1), there was no apparent myelin loss around ORO+ macrophages although these cells contained material stained with antibodies against myelin basic protein (MBP) epitopes and neoepitopes. However, patchy myelin loss was detectable around the phagocytic macrophages uniformly distributed throughout group 2 plaques. ORO+ macrophages containing MBP peptides were confined to the hypercellular border of group 4 lesions, in which the demyelinating process may be recurrent.
Insights
This study identifies phagocytic cells in multiple sclerosis (MS) lesions, revealing microglial activation and macrophage roles in demyelination at different disease stages.
Area of Science:
- Neuroimmunology
- Pathology
Background:
- Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by demyelination.
- Understanding the cellular dynamics within MS lesions is crucial for developing targeted therapies.
Purpose of the Study:
- To quantitatively analyze phagocytic cell populations and their relationship with myelin degradation in active and chronic MS plaques.
- To characterize the phenotypes and distribution of macrophages and microglia during different stages of demyelination in MS.
Main Methods:
- Quantitative immunocytochemical analysis of macrophage markers and myelin degradation products.
- Serial cryostat sectioning of 10 MS cases.
- Staining for HLA-DQ, alpha 1-antichymotrypsin, Ber-MAC3, RFD7, and oil red O (ORO).
Main Results:
- Class II antigen HLA-DQ identified activated microglia in actively demyelinating lesions.
- Perivascular monocytes and myelin-laden macrophages (Ber-MAC3+, RFD7+) were observed.
- Oil red O+ phagocytes containing myelin basic protein (MBP) peptides indicated myelin degradation, with distribution varying by lesion stage.
Conclusions:
- Phagocytic cells, including activated microglia and macrophages, play distinct roles in the dynamic process of demyelination in MS.
- The distribution and phenotype of these cells correlate with lesion stage, suggesting a temporal progression of phagocytosis and myelin clearance.