An essential aspect of innate immunity is recognition of molecular patterns on the surface of pathogens or altered self through the lectin and classical pathways, two of the three well-established activation pathways of the complement system. This recognition causes activation of the MASP-2 or the C1s serine proteases followed by cleavage of the protein C4. Here we present the crystal structure...

The fourth component of complement (C4) was found to incorporate radiolabel from [35S]O4 during synthesis in murine peritoneal macrophages and the human hepatoma-derived cell line, HepG2. The sulfate label was localized to the COOH-terminal autolytic fragment of the C4 alpha-chain. No label was seen associated with intracellular pro-C4. The structurally similar third and fifth components of com...

Elevation of plasma inflammatory factors in major depressive disorder (MDD) has been repeatedly observed, but contradictory results have also been reported. Alteration of complement components in MDD may also contribute to the pathophysiology of MDD by participating in inflammation. The recent findings that complement component 4 (C4) was involved in neural synapse elimination and associated wi...

The S region of the H-2 complex controls the serum levels of two proteins, Ss and Sip, which are closely related antigenically (1-4). Several observations suggest that the Ss protein may be part of the complement system and homologous to C4. F(ab')2 fragments of antibody to Ss inhibit the hemolytic activity of mouse serum (5) and Ss antigenic determinants are incorporated into immune complexes ...

Levels of circulating IgE, total haemolytic complement, and components C4 and C3 were measured in 16 asthmatics with aspirin idiosyncrasy and in control subjects. IgE levels were mostly within normal limits. No differences were found between the complement profiles-in particular the C4 levels-in the two groups. As low levels of C4 have been found in patients with intrinsic asthma, these results...

Complement component C4 (C4) is a highly variable complement pathway gene situated ∼500 kb from DRB1 and DQB1, the genes most strongly associated with many autoimmune diseases. Variations in C4 copy number (CN), length, and isotype create a highly diverse gene cluster in which insertion of an endogenous retrovirus in the ninth intron of C4, termed HERV-K(C4), is a notable component. We investig...

Deficiencies of early components of the classical complement pathway are known to be associated with systemic lupus erythematosus (SLE). C4 null alleles, C4A Q0 and C4B Q0, are prime candidates for the major histocompatibility complex associated factor which determines susceptibility to SLE. There is poor correlation, however, between the presence of low concentrations of C4 and possession of C...

Hepatocytes which had been isolated from the livers of Charles River rats were cultured in vitro. The cells were shown to synthesize albumin and the complement components C4, C2, C3 and B. Pulse-label studies with [35S]methionine showed that C4 and C3 were synthesized as single polypeptide chains. Pro-C4 did not appear to be converted into the plasma form of C4 intracellularly, whereas cell lys...

The prediction and verification of adaptive trajectories on macroevolutionary timescales have rarely been achieved for complex biological systems. Employing a model linking biological information at multiple scales, Heckmann et al. simulate likely sequences of evolutionary changes from C3 to C4 photosynthesis biochemistry.

studies were undertaken to evaluate content of igg, igm, c3, c4, ch50 and proteines of sera from 53 drug addicts by immunological methods. results shows an increase of igg and no significant variatrion in the level of other ig(s). in the same time we have seen an augmentation of gamma globuline in the protein electrophoresis pattern. the level of c3 and c4 of complement component rest unchanged.