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CR1 stump peptide and terminal complement complexes are found in the glomeruli of lupus nephritis patients
J E Teixeira1, R S Costa, P J Lachmann
1Department of Parasitology, Microbiology and Immunology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
Insights
Severe lupus nephritis reduces complement receptor 1 (CR1) on podocytes. This decrease in CR1 on kidney cells is linked to complement system activation and proteolysis, indicated by CR1 stumps in biopsies.
Area of Science:
- Nephrology
- Immunology
- Pathology
Background:
- Complement receptor 1 (CR1) is crucial for kidney health.
- Reduced CR1 on podocytes is observed in severe nephropathies, particularly diffuse proliferative glomerulonephritis (DPGN) in systemic lupus erythematosus (SLE).
- CR1 reduction on erythrocytes is linked to proteolysis by activated macrophage proteases.
Purpose of the Study:
- To investigate the presence of terminal complement complex (TCC) and CR1 stumps in SLE kidney biopsies.
- To correlate CR1 levels and TCC deposition with the severity of glomerular lesions in lupus nephritis.
Main Methods:
- Indirect immunoperoxidase staining of kidney biopsy sections from SLE patients.
- Detection of terminal complement complex (TCC) and CR1 stump peptides.
- Histological analysis of glomerular lesions (mesangial vs. mixed patterns).
Main Results:
- TCC deposits were found in mesangium (less severe lesions) and mesangium/capillary loops (more severe lesions).
- Patients with active DPGN showed reduced intact podocyte CR1 and increased CR1 stumps.
- A correlation was observed between CR1 reduction, CR1 stumps, TCC deposition, and severe glomerular damage in SLE.
Conclusions:
- The decrease in podocyte CR1 in severe SLE glomerular lesions may result from local proteolytic activity.
- Complement system activation and TCC deposition are implicated in CR1 degradation in lupus nephritis.
- CR1 stumps serve as a marker for CR1 proteolysis in active lupus nephritis.
Abstract:
The number of CR1 on podocytes is reduced in nephropathies with severe glomerular damage, especially in the diffuse proliferative glomerulonephritis (DPGN) of systemic lupus erythematosus (SLE). Reduction of CR1 number on erythrocytes is due to proteolysis of CR1 by macrophage proteases activated by the reaction of their complement receptors, which leaves a 'CR1 stump peptide' on the erythrocyte. In the present study, we demonstrated the presence of the terminal complement complex (TCC) and the CR1 stump in histological sections of biopsies from patients with SLE by the indirect immunoperoxidase technique. Less severe glomerular lesions presented TCC deposits mainly in the mesangium (mesangial pattern). In lupus nephritis, with more severe glomerular damage, TCC deposits were detected both in the mesangium and in the capillary loops with podocyte involvement (mixed pattern). Patients with highly active DPGN presented a marked reduction of intact podocyte CR1 receptors in association with increased reactivity to the anti-CR1 stump antibody and with glomerular TCC deposits of mixed histological pattern. These results suggest that the decrease in the number of podocyte CR1 receptors in severe glomerular lesions of SLE may be due to a local proteolytic activity associated with activation and deposition of TCC.