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Endothelium myeloperoxidase-antimyeloperoxidase interaction in vasculitis
M Vargunam1, D Adu, C M Taylor
1Renal Research Laboratory, Queen Elizabeth Hospital, Birmingham, UK.
Abstract:
Antibodies to myeloperoxidase (MPO) are found in the sera of patients with microscopic polyarteritis and idiopathic crescentic glomerulonephritis. Their pathogenicity is unknown. Studies were carried out on the binding of MPO to cultured human umbilical vein endothelial cells and the recognition of endothelium-bound MPO by antibody to MPO. Endothelial cells were cultured from human umbilical veins. The binding of MPO to endothelial cells and its inhibition by poly-D-lysine was detected using a monoclonal antibody to MPO and direct staining with APAAP and also by an enzyme-linked immunoassay (ELISA). The binding of anti-MPO antibody in the sera of patients with microscopic polyarteritis to endothelium-coated MPO was detected by ELISA. MPO bound to endothelial cells both on direct staining and ELISA and this binding was inhibited by the polycation poly-D-lysine, suggesting that it was charge mediated. Binding of anti-MPO antibody in the sera of patients with microscopic polyarteritis to endothelium-coated MPO was significantly higher than the binding of sera from normal subjects (P = 0.04), patients with idiopathic glomerulonephritis (P = 0.0005), and patients with lupus nephritis (P = 0.009). MPO binds to cultured human umbilical vein endothelium probably by a charge mechanism, and can react with anti-MPO antibodies in the sera of patients with microscopic polyarteritis as well as with a mouse monoclonal anti-MPO antibody. This binding of anti-MPO antibody to MPO fixed to the endothelial cell surface provides a mechanism by which endothelial injury and inflammation might occur in microscopic polyarteritis.
Insights
Antibodies to myeloperoxidase (MPO) bind to endothelial cells, potentially causing inflammation. This binding is significantly higher in patients with microscopic polyarteritis, suggesting a role in disease pathogenesis.
Area of Science:
- Immunology
- Nephrology
- Pathology
Background:
- Antibodies to myeloperoxidase (MPO) are detected in patients with microscopic polyarteritis and idiopathic crescentic glomerulonephritis.
- The pathogenic role of these anti-MPO antibodies in vasculitis remains unclear.
Purpose of the Study:
- To investigate the binding of MPO to human umbilical vein endothelial cells.
- To determine if anti-MPO antibodies recognize MPO bound to endothelial cells.
- To explore the potential mechanism of endothelial injury in microscopic polyarteritis.
Main Methods:
- Cultured human umbilical vein endothelial cells were used.
- Enzyme-linked immunoassay (ELISA) and direct staining (APAAP) detected MPO binding.
- Binding inhibition studies using poly-D-lysine were performed.
- ELISA measured anti-MPO antibody binding in patient sera (microscopic polyarteritis, glomerulonephritis, lupus nephritis) and normal subjects.
Main Results:
- Myeloperoxidase (MPO) demonstrated binding to endothelial cells, inhibited by poly-D-lysine, indicating charge-mediated attachment.
- Anti-MPO antibodies from microscopic polyarteritis patients showed significantly higher binding to endothelium-bound MPO compared to controls.
- Binding was significantly higher than in patients with idiopathic glomerulonephritis and lupus nephritis.
Conclusions:
- Myeloperoxidase binds to cultured human umbilical vein endothelium via a charge-dependent mechanism.
- This binding allows MPO to be recognized by anti-MPO antibodies present in patients with microscopic polyarteritis.
- This interaction provides a potential mechanism for endothelial damage and inflammation in microscopic polyarteritis.