Functional consequences of the genetic polymorphism of the third component of complement.
The third component of complement, the central protein of the complement cascade, occurs in two principal allotypes, C3S and C3F. An excess frequency of the F allotype has been implicated in a number of disease states, including some forms of glomerulonephritis. These associations have been explained by functional differences between C3S and C3F. We examined several complement functions, using purified preparations of C3S or C3F. The C3S allotype was 1.3 times more efficient than C3F in a hemolytic assay employing sensitized sheep erythrocytes; this difference was shown to arise from a slightly more efficient deposition of C3F on the cell surface. These differences are trivial and of much less magnitude than the functional differences between C4A and C4B. There were no differences between allotypes in their ability to be converted to inactive C3b (C3bi) by complement factors H and I or by CR1 and factor I. No significant differences were seen between the allotypes and their ability to support solubilization of preformed immune complexes.
Welch
T R
TR
Department of Pediatrics, University of Cincinnati College of Medicine, Ohio.
Beischel
L
L
Kleesattel
A
A
D000818:Animals; D000936:Antigen-Antibody Complex / Q000235:genetics; D001798:Blood Proteins / Q000032:analysis; D002417:Cattle; D003176:Complement C3 / Q000032:analysis / Q000235:genetics*; D003180:Complement C3b Inactivator Proteins / Q000494:pharmacology; D003181:Complement C4 / Q000032:analysis; D017242:Complement Factor H; D017244:Complement Factor I; D004912:Erythrocytes / Q000276:immunology; D006461:Hemolysis / Q000235:genetics; D006801:Humans; D010641:Phenotype; D011110:Polymorphism, Genetic; D011817:Rabbits; D012697:Serine Endopeptidases / Q000494:pharmacology; D012756:Sheep; D012995:Solubility
D000936:Antigen-Antibody Complex; D001798:Blood Proteins; C493495:CFH protein, human; D003176:Complement C3; D003180:Complement C3b Inactivator Proteins; D003181:Complement C4; D017242:Complement Factor H; D012697:Serine Endopeptidases; D017244:Complement Factor I