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Complement system promotes transfer of immune complex across glomerular filtration barrier
Y Fujigaki1, S R Batsford, D Bitter-Suermann
1Institut für Medizinische Mikrobiologie und Hygiene, Abteilung Immunologie, Germany.
Summary
The complement system aids immune complex (IC) movement across kidney membranes. Complement depletion slows IC transfer, indicating its crucial role in clearing deposited immune complexes.
Area of Science:
- Immunology
- Nephrology
- Complement System Biology
Background:
- The fluid-phase solubilizing effect of complement (C) on immune complexes (IC) is established.
- Tissue-deposited IC movement across the glomerular basement membrane (GBM) remains less understood.
- This study investigates C's role in IC translocation within the GBM.
Purpose of the Study:
- To determine the influence of complement depletion on the migration of immune complexes (IC) across the glomerular basement membrane (GBM).
- To analyze the effect of complement and polymorphonuclear leukocytes (PMNs) on IC distribution in a rat model of passive in situ IC nephritis.
Main Methods:
- Rats were C-depleted or PMN-depleted.
- Kidneys were perfused with cationized ferritin (tracer antigen) followed by anti-ferritin antibody.
- Glomerular distribution of antigen, antibody, and C3 was assessed using immunogold staining.
Main Results:
- In intact rats, IC shifted from subendothelial to subepithelial within 48 hours.
- C-depleted rats showed delayed IC transfer, with some remaining subendothelial at 24 and 7 days.
- PMN depletion did not alter IC distribution, but reduced proteinuria, as did C depletion.
Conclusions:
- The complement system significantly promotes the transfer of immune complexes across the glomerular basement membrane.
- Complement's solubilizing effect on IC lattices is likely responsible for enhanced IC clearance.
- Glomerular permeability alone does not ensure rapid and complete IC movement.