Depressing hepatic macrophage complement receptor function causes increased susceptibility to endotoxemia and...

Area of Science:

• Immunology
• Pathophysiology
• Host Defense Mechanisms

Background:

• Previous studies indicated that thermal injury depresses in vivo hepatic macrophage complement receptor clearance function.
• The significance of this impaired complement receptor function in host defense remains to be fully elucidated.

Purpose of the Study:

• To investigate the impact of depressed complement receptor function on susceptibility to endotoxin shock and bacterial infection in uninjured animals.
• To determine if complement receptor impairment is a critical factor in host defense.

Main Methods:

• Hepatic complement receptor clearance function was assessed by measuring the uptake of immunoglobulin M (IgM) or immunoglobulin G (IgG) coated erythrocytes in rats.
• Depression of this function was induced by injecting varying doses of IgG-coated erythrocytes (EIgG).
• Susceptibility to endotoxin shock and Pseudomonas aeruginosa infection was evaluated following EIgG administration.

Main Results:

• Injection of higher doses of EIgG (8.7 X 10(8) or 17.4 X 10(8)/100 g) significantly depressed hepatic complement receptor clearance function.
• This depression was not attributable to reduced hepatic blood flow or C3 depletion.
• Increased susceptibility to endotoxin shock and P. aeruginosa infection correlated with the dose of EIgG administered.

Conclusions:

• Depression of hepatic macrophage complement receptor clearance function, induced by EIgG, compromises host defense.
• Impaired complement receptor function is a significant factor in increased susceptibility to endotoxin shock and bacterial infections.