Circulating immune-complexes and complement activation through the classical pathway in...

Area of Science:

• Nephrology
• Immunology
• Complement System Biology

Background:

• Anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN) is a severe kidney disease.
• Complement system activation is implicated in AAGN, but the specific pathway remains unclear.

Purpose of the Study:

• To investigate the role of complement activation pathways in myeloperoxidase (MPO)-AAGN.
• To determine the relationship between ANCA affinity, circulating immune-complexes (CICs), and complement activation in MPO-AAGN.

Main Methods:

• Retrospective analysis of 20 MPO-AAGN patients.
• Assessed serum CICs, C5a, C5b-9, and classical pathway activation.
• Evaluated ANCA affinity and complement component deposition in renal tissue via immunofluorescence.

Main Results:

• Circulating immune-complexes (CICs) were detected in 65% of patients, all with high-affinity ANCAs.
• Elevated serum C5a and C5b-9 levels correlated positively with CIC levels.
• Glomerular deposition of C4d, C5, and C5b-9 was observed, with minimal alternative pathway component deposition.

Conclusions:

• Results indicate immune-complex-induced complement activation via the classical pathway contributes to MPO-AAGN pathogenesis.
• High-affinity ANCAs and CICs are associated with classical pathway activation in MPO-AAGN.