In Vitro Studies of Complement Function in Sera of C4-Deficient Guinea Pigs

Abstract

In vitro studies were performed utilizing sera from a strain of guinea pigs with a total absence of hemolytically active C4. Previous studies in these animals have demonstrated normal complement-dependent inflammatory reactions, suggesting that they are able to bypass their deficiency of C4. In vitro studies with C4-deficient serum also indicate normal activation of late-acting C components. Thus, endotoxin was capable of fixing normal amounts of the late components of complement (C3-9) in these sera, but did not fix C1 and C2. Antigen-antibody complexes fixed both early and late components of complement, although components beyond C4 were fixed less efficiently than in normal sera. Therefore, both in vivo and in vitro evidence indicates that the C4-deficient guinea pigs possess an alternate pathway for activation of late-acting complement components. Antigenic analysis of C4-deficient serum utilizing both guinea pig anti-C4 antibody and rabbit anti-C4 antibody suggests an absolute deficiency of C4-like molecules. Sera from animals with C4-deficiency were found to have one-half the normal level of C2. Sera from five of eight animals tested had 10–20% normal C1 activity. C3-9 assayed as a complex was normal.

Interactions of the Classical and Alternate Complement Pathway with Endotoxin Lipopolysaccharide EFFECT ON PLATELETS AND BLOOD COAGULATION

“…Incubation of the sera of these animals with endotoxin leads to consumption of the late components of complement (8). Since the C4D ani-' mals have a complete block in function of the classical complement pathway, these studies (8) ternate complement pathway and produces its biological effects by this means.…”

“…These studies were made possible by the availability of guinea pigs with a genetically controlled inability to synthesize C4, one of the early components in the classical complement pathway (12). Incubation of the sera of these animals with endotoxin leads to consumption of the late components of complement (8). Since the C4D ani-' mals have a complete block in function of the classical complement pathway, these studies (8) ternate complement pathway and produces its biological effects by this means.…”

“…3 toxin-treated normal animals 52±-8% (8), endotoxin-treated C4D animals 41±-3% (8), saline-treated normal animals 139±-6% (8), saline-treated C4D animals 135+30%o, (8) CVF-treated normal animals given endotoxin 25±1%o (5). Normal Effect of endotoxin on the clotting time in C4D guinea pigs with reconstituted C4 levels.…”

“…No differences in the initial platelet and WBC counts were noted between the normal and C4D animals; mean platelet counts were 744,000-+SD 103,000 and 760,000+-SD 201,000 respectively, mean WBC counts were 9,000+SD 2870 and 9,300+SD 1650. (8), saline-treated C4D animals 106±11.6% (8), CVFtreated normals given endotoxin 95±5% (5).…”

“…The alternate or properdin pathway acts through another series of proteins to enter the complement sequence at the C3 step (8)(9)(10)(11). In defining the role of these two pathways, this study utilized the recently described strain of guinea pigs with a genetically controlled deficiency in C4 (C4D)' (12).…”