Inhibition of complement alternative pathway function with anti-properdin monoclonal antibodies.

Area of Science:

• Immunology
• Complement System Biology

Background:

• Complement activation products are implicated in inflammatory diseases.
• The distinct roles of classical and alternative complement pathways in pathology remain unclear.
• Existing complement inhibitors often affect both pathways, limiting specific therapeutic development.

Purpose of the Study:

• To investigate the specific role of the alternative complement pathway in inflammatory conditions.
• To develop targeted inhibitors for the alternative complement pathway.
• To assess the therapeutic potential of inhibiting the alternative pathway.

Main Methods:

• Development of monoclonal antibodies targeting human properdin to inhibit alternative pathway function.
• In vitro assessment of antibody efficacy in blocking alternative pathway activation.
• Evaluation of anti-properdin antibody effects in a cardiopulmonary bypass model using human blood.
• Measurement of complement activation products (C3a, C5b-9) and inflammatory markers (neutrophil, platelet activation).

Main Results:

• Monoclonal antibodies specifically inhibited alternative pathway function in vitro.
• Anti-properdin antibody treatment in a cardiopulmonary bypass model nearly abolished C3a and C5b-9 formation.
• The antibody significantly reduced neutrophil and platelet activation in the bypass model.
• Surprisingly, the antibody also inhibited C5b-9 generation triggered by classical pathway activators, indicating alternative pathway involvement.

Conclusions:

• The alternative complement pathway plays a substantial role in complement-mediated inflammation.
• Targeted inhibition of the alternative pathway, via anti-properdin antibodies, is a promising therapeutic strategy.
• The alternative pathway significantly contributes to complement activation even when the classical pathway is initially triggered.