We examined the interaction of complement component C3 with surface molecules on Trypanosoma cruzi. Five- to six-fold more C3 was bound to epimastigotes (Epi) than to metacyclic trypomastigotes (CMT) of strain M88. Epi and CMT were surface iodinated, then incubated in C8-deficient serum, and detergent lysates were applied to anti-C3 antibody that had been coupled to Sepharose. We found that 9.2...

Two complex enzymes were assembled that both converted C3 to C3b, one consisting of activated properdin (P), native C3, proactivator (PA) and proactivator convertase (PAase), and the other of nephritic factor (NF) and the same three cofactors. By maintaining a critical concentration of PAase, the P-C3 convertase and the NF-C3 convertase were shown to function efficiently without formation of th...

BACKGROUND Myocardial infarction (MI) is a major clinical problem because of its large contribution to mortality. The genetic bases of this disease have been widely studied in recent years to find a clear association with some genetic markers that increase the risk of its occurrence. In the present investigation, the correlation between MI and the C3 complement polymorphism was analyzed using a...

C3-bearing immune complexes and C3 activation products were detected by using two monoclonal antibodies, one specific for a neoantigenic determinant on C3c and the other for C3d. To quantitate immune complexes, the anti-C3c or anti-C3d antibodies were fixed to microtiter plates and reacted with test plasma. The binding of C3-bearing immune complexes in this plasma was then measured with radiois...

OBJECTIVE For the inflammation characteristic of rheumatoid arthritis, the relative contribution of mediators produced locally in the synovium versus those circulating systemically is unknown. Complement factor C3 is made in rheumatoid synovium and has been proposed to be a crucial driver of inflammation. The aim of this study was to test, in a mouse model of rheumatoid arthritis, whether C3 sy...

The present paper describes the purification and characterization of a major serum protein of the rainbow trout (Salmo gairdneri) required for complement-related functions (target cell lysis and opsonization). This protein, termed C3-1, was identified as the third component (C3) of rainbow trout complement. It is homologous to component C3 of human and other mammalian complements based on its s...

Complement-mediated opsonization of bacteria by C3 binding is an important component of the host innate immune system. Little information is available concerning the interaction between complement proteins and capsule type 5 and 8 Staphylococcus aureus strains, even though these isolates are responsible for approximately 70% of human staphylococcal infections. To investigate the importance of a...

Quantitation of the C3 component of complement by single radial immunodiffusion is subject to error because the C3 molecule has several antigenic determinants and anti-C3 sera differ in their specificity to these determinants. C3 was measured in plasma (ethylenediaminetetraacetate anticoagulant) and serum, in five normal individuals, by use of four such commercial kits. The effects of ethylened...