Specific inactivation of the fourth complement component. I. In vivo studies

Area of Science:

• Immunology
• Complement System Biology

Background:

• The complement system plays a crucial role in immune responses and inflammatory processes.
• Complement-dependent immune injuries are implicated in various pathological conditions.

Purpose of the Study:

• To investigate the effect of inhibiting the fourth complement component (C4) on Arthus reactions in guinea pigs.
• To determine if early interruption of the complement cascade can prevent complement-dependent immune injury.

Main Methods:

• Intravascular injection of a specific C4 inactivator from shark serum into guinea pigs.
• Assessment of Arthus reactions (passive and direct) through gross and histological observations.
• In vitro experiments demonstrating immune precipitate inactivation by complement.

Main Results:

• Severe and prolonged depletion of serum C4 was achieved in treated guinea pigs.
• Arthus reactions were significantly suppressed or absent in C4-inactivated animals.
• In vitro studies confirmed functional inactivation of immune complexes by complement.

Conclusions:

• Interruption of the complement cascade at the C4 step effectively suppresses complement-dependent immune injury.
• Temporary complement inactivation demonstrates potential therapeutic benefits for immune-mediated diseases.
• Further investigation into C4 depletion's impact on C5a generation and immune complex saturation is warranted.