Complement in ANCA-associated vasculitis: mechanisms and implications for management

Area of Science:

• Immunology
• Nephrology
• Autoimmune Diseases

Background:

• Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a severe autoimmune condition characterized by kidney inflammation (pauci-immune necrotizing crescentic glomerulonephritis).
• The complement system was initially overlooked in AAV pathogenesis due to minimal immunoglobulin and complement deposition observed in kidney biopsies.

Purpose of the Study:

• To review the clinical, in vivo, and in vitro evidence supporting the role of complement activation in AAV development.
• To explore therapeutic strategies targeting the complement system for AAV treatment.

Main Methods:

• Review of existing scientific literature, including clinical observations and experimental data from animal models and in vitro studies.
• Analysis of the role of complement activation products, specifically C5a, in neutrophil activation and its link to coagulation.

Main Results:

• Evidence indicates that complement system activation, especially the alternative pathway, is critical for AAV pathogenesis.
• The complement activation product C5a is identified as a central mediator, stimulating neutrophils and bridging inflammation with coagulation via thrombin generation.
• ANCA and C5a co-stimulation leads to neutrophil respiratory burst, degranulation, and activation of the coagulation cascade.

Conclusions:

• Complement activation, driven by the alternative pathway and C5a, is integral to the development of ANCA-associated vasculitis.
• Targeting the complement system presents a promising therapeutic avenue for managing AAV.