Complement-independence of the acute-phase production of serum amyloijd P-component (SAP) in mice.

Mice depleted of circulating C3 by injection of cobra factor (CoF), the C3-activating protein of cobra (Naja naja) venom, mounted the same acute-phase responses of serum amyloid P-component (SAP) to subsequent injection of casein, bacterial lipopolysaccharide or croton oil as did normal control mice. There was also evidence for accelerated synthesis of C3 itself in response to injection of these acute-phase stimulants in CoF-treated mice. On the other hand complement activation produced by injection of CoF alone did not cause any elevation of the serum SAP level. These results indicate that acute-phase plasma protein production can proceed independently of the complement system as a mediator of or participant in inflammatory reactions, and that complement activation alone is not a sufficient stimulus for an acute-phase response, at least of SAP.