Cardiopulmonary bypass and complement activation. Involvement of classical and alternative pathways

Area of Science:

• Immunology
• Cardiovascular Surgery

Background:

• Cardiopulmonary bypass (CPB) is a critical procedure in cardiac surgery.
• The complement system is a vital part of innate immunity.
• CPB may trigger immune responses, including complement activation.

Purpose of the Study:

• To investigate complement system activation during CPB.
• To identify complement components consumed during CPB.
• To determine the pathway of complement activation and the effect of steroid therapy.

Main Methods:

• Analysis of complement components (C3, C4, factor B) in patient sera.
• Comparison between bubble and membrane oxygenators.
• Assessment of steroid therapy's impact on complement activation.

Main Results:

• Complement activation was observed during CPB, with significant consumption of C3, C4, and factor B.
• Both bubble and membrane oxygenators induced complement activation.
• Steroid therapy did not attenuate complement activation.
• Evidence suggests predominant activation via the classical pathway, potentially linked to IgM aggregates.

Conclusions:

• Cardiopulmonary bypass robustly activates the complement system.
• Complement activation during CPB is independent of steroid administration.
• The classical pathway is likely the primary route of activation, possibly influenced by IgM.
• Further research into mitigating complement activation during CPB is warranted.