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Distribution of macrophages in rheumatoid synovial membrane and its association with basic activity
Abstract:
Rheumatoid arthritis (RA) is an inflammatory disease of the synovial membrane, which results in the destruction of joints by inflammatory pannus. The synovial membrane shows proliferation and cellular infiltrates on microscopy with signs of chronic and acute inflammation. Macrophages are thought to play a central role in the pathogenesis of RA. We examined synovial membrane specimens of 21 RA patients using morphological, immunohistological and enzyme histochemical methods for number and distribution of macrophages. We were able to identify 41.5 +/- 8.8% of lining cells as macrophages, depending on the method used. In abundant diffuse lymphocellular infiltrates, 23.4 +/- 11.1% of mononuclear cells were macrophages. In addition, most cells in the region of tumorlike proliferation and a stromal population of fibroblastlike cells were detected by macrophage markers. Although cell number in synovial membrane increases drastically, we did not find correlations between the relative amount of macrophages in these regions and basic activity. Basic activity includes proliferative reaction as well as lymphoplasmacellular and mononuclear infiltration--both signs of an immunopathological process. In contrast, using enzymes or activation markers, there was a clear correlation. We consider that a constant high percentage of macrophages in RA synovial membrane is present regardless of any actual inflammatory process.
Insights
Macrophages are consistently abundant in rheumatoid arthritis (RA) synovial membranes, irrespective of active inflammation. This study quantifies macrophage presence in RA joint tissues, revealing their significant role in disease pathogenesis.
Area of Science:
- Immunology
- Pathology
- Rheumatology
Background:
- Rheumatoid arthritis (RA) is a chronic inflammatory joint disease.
- RA involves synovial membrane inflammation and joint destruction by pannus.
- Macrophages are implicated in RA pathogenesis.
Purpose of the Study:
- To quantify the number and distribution of macrophages in RA synovial membrane specimens.
- To investigate the correlation between macrophage presence and disease activity markers.
Main Methods:
- Morphological, immunohistological, and enzyme histochemical analysis of 21 RA patient synovial specimens.
- Quantification of macrophages in lining cells, infiltrates, and stromal populations.
- Assessment of correlations with basic disease activity and activation markers.
Main Results:
- Macrophages constituted 41.5% of lining cells and 23.4% of mononuclear cells in infiltrates.
- Macrophage markers identified cells in proliferative regions and stromal fibroblast-like populations.
- No correlation found between macrophage percentage and basic disease activity.
- Clear correlation observed between macrophage presence and enzyme or activation markers.
Conclusions:
- A consistently high percentage of macrophages is present in RA synovial membranes.
- Macrophage presence is largely independent of the current inflammatory state.
- Macrophages play a significant, persistent role in rheumatoid arthritis synovial tissue.