Serum C1q, C3, C4, and C5 components of complement levels were measured in 56 healthy subjects and 98 patients with trachoma. Serum C1q and C3 levels were found to be significantly low in stages II and III. There was no change in serum C4 and C5 levels in any of the stages. The levels of C1q and C3 complement components in serum in stages II and III returned to normal as the disease resolved fo...

Polysomes (S-20) from homogenates of guinea pig liver synthesized serum albumin and a precursor of the fourth component of guinea pig complement (C4) in vitro. The C4 precursor (pro-C4) accounted for approximately 0.2% and albumin 4% of the radiolabeled protein precipitable by trichloroacetic acid and not bound to polysomes. Pro-C4 is a single polypeptide chain (molecular weight 200,000) which ...

A 22 year old woman with systemic lupus erythematosus affecting the central nervous system had acquired C1 inhibitor deficiency. She was admitted for treatment of psychotic behaviour, but showed no signs of angioedema. The serum complement profile of the patient showed normal C3 concentration and a depletion of C4, C2, C1 inhibitor, and C1q. Her parents had normal complement profiles. An extrem...

Guinea pigs genetically deficient in the second (C2) or fourth component of complement (C4) generally appear healthy in contrast to humans with a C2 or C4 deficiency. However, upon investigation of these genetic deficiencies in guinea pigs for signs of dysregulation in the humoral immune system and especially autoantibodies, many complement-deficient guinea pigs (greater than 50%) had elevated ...

The classical pathway of complement is crucial to the immune system, but it also contributes to inflammatory diseases when dysregulated. Binding of the C1 complex to ligands activates the pathway by inducing autoactivation of associated C1r, after which C1r activates C1s. C1s cleaves complement component C4 and then C2 to cause full activation of the system. The interaction between C1s and C4 i...

Serum C1q, C3, C4, and C5 components of complement levels were measured in 35 healthy subjects and 29 patients with acute conjunctivitis due to adenovirus type 2, 7, and 8 infections. Serum C1q and C3 levels were found to be significantly low, and there was no change in serum C4 and C5 levels. A progressive decline in the serum complement level with the severity of disease was observed. The cha...

The complement system enhances antibody responses to T-dependent antigens, but paradoxically, deficiencies in C1 and C4 are strongly linked to autoantibody production in humans. In mice, disruption of the C1qa gene also results in spontaneous autoimmunity. Moreover, deficiencies in C4 or complement receptors 1 and 2 (CR1/CR2) lead to reduced selection against autoreactive B cells and impaired h...