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Immune complex degradation by cultured rat mesangial cells
1Department of Pathology, University of Leicester, U.K.
Abstract:
The binding and degradation of radiolabelled immune complexes by cultured rat glomerular mesangial cells were measured and compared with the binding and degradation by thioglycollate-elicited rat peritoneal macrophages. Mesangial cells are generally considered to be a modified pericyte with smooth muscle-like properties, but they were able to bind and degrade soluble immune complexes at rates comparable to those of the macrophages. In a second study, the ability of cultured mesangial cells to bind and degrade immune complexes of varying molecular weight was assessed. Very large, insoluble complexes were found to bind to mesangial cells more avidly than small soluble complexes, but unlike the small complexes, the large complexes did not appear to undergo degradation. These findings support a role for the intrinsic mesangial cell in the elimination of small soluble immune complexes as they arrive in the glomerulus. They also provide a possible explanation for the paradox that large immune complexes--i.e., electron-dense deposits--can persist in the mesangium next to the intrinsic mesangial cells without being rapidly destroyed.
Insights
Cultured rat glomerular mesangial cells bind and degrade soluble immune complexes similarly to macrophages. Large immune complexes bind but are not degraded, explaining their persistence in the glomerulus.
Area of Science:
- Nephrology
- Immunology
- Cell Biology
Background:
- Glomerular mesangial cells are specialized pericytes with smooth muscle-like characteristics.
- The role of mesangial cells in clearing immune complexes within the glomerulus is not fully understood.
Purpose of the Study:
- To compare the capacity of cultured rat glomerular mesangial cells and macrophages to bind and degrade immune complexes.
- To investigate how mesangial cells handle immune complexes of different sizes and solubility.
Main Methods:
- Radiolabelled immune complexes were used to quantify binding and degradation.
- Cultured rat glomerular mesangial cells and thioglycollate-elicited rat peritoneal macrophages were utilized.
- Immune complexes of varying molecular weights were tested for mesangial cell interaction.
Main Results:
- Mesangial cells demonstrated binding and degradation rates for soluble immune complexes comparable to macrophages.
- Mesangial cells bound large, insoluble immune complexes more avidly than small, soluble ones.
- Degradation of large, insoluble immune complexes by mesangial cells was not observed.
Conclusions:
- Intrinsic mesangial cells play a significant role in eliminating small, soluble immune complexes in the glomerulus.
- The differential handling of immune complexes based on size and solubility by mesangial cells may explain the persistence of large immune deposits in the mesangium.