Effect of complement depletion on lung fluid balance after thrombin

Area of Science:

• Pulmonary Medicine
• Immunology
• Physiology

Background:

• Pulmonary thromboembolization (PT) can lead to increased lung vascular permeability.
• The role of the complement system in this process is not fully understood.

Purpose of the Study:

• To investigate the effect of complement depletion on lung fluid and protein exchange following thrombin-induced pulmonary thromboembolization.

Main Methods:

• Sheep with lung lymph fistulas were used to measure pulmonary transvascular fluid and protein dynamics.
• Three groups were studied: pulmonary thromboembolization alone, complement depletion followed by pulmonary thromboembolization, and increased left atrial pressure.
• Complement was depleted using cobra venom factor (CVF).

Main Results:

• Thrombin infusion increased pulmonary lymph flow (Qlym) and lymph-to-plasma protein ratio (L/P) in normal sheep.
• In complement-depleted sheep, thrombin caused a transient increase in Qlym with a decrease in L/P.
• Increased left atrial pressure (Pla) exacerbated Qlym increase without changing L/P in normal sheep, but decreased L/P in complement-depleted sheep.

Conclusions:

• The complement system plays a significant role in increasing lung vascular permeability after thrombin-induced microembolization.
• Complement activation contributes to the protein leak observed in pulmonary thromboembolization.