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PubMed2001

C1-inhibitor deficiency and angioedema.

C1-inhibitor deficiency can be inherited or acquired; both conditions lead to recurrent angioedema that can be life threatening when the larynx is involved (hereditary angioedema, HAE; acquired angioedema, AAE). The genetic defect is due to the heterozygous deficiency of C1-Inh that is transmitted as an autosomal dominant trait. Mutations causing HAE have been found distributed over all exons and splice sites of C1-Inh structural gene: only a few of them have been found more than once. Depending on DNA defect, C1-Inh is not transcribed, or not translated or not secreted. Finally, in 15% of HAE patients, an antigenically normal, but non-functional C1-Inh is present in serum (HAE type II). C1-Inh deficiency can be acquired, due to an accelerated consumption. Such an accelerated consumption can depend on circulating autoantibodies that bind C1-Inh causing its inactivation and catabolism; or to associated diseases, usually lymphoproliferative diseases, that consume C1-Inh with different mechanisms. Effective therapies can prevent or revert angioedema symptoms in C1-Inh deficiency, the main problem of this condition remaining misdiagnosis. The common knowledge that angioedema is an allergic symptom frequently prevents a correct diagnostic approach: C1-Inh deficiency goes unrecognized and the disease can still be lethal. Correct prophylactic treatment is based on attenuated androgens in HAE and on antifibrinolytic agents in AAE. Life threatening laryngeal attacks and severe abdominal attacks are effectively reverted, in both conditions, with C1-Inh plasma concentrate. A special remark to this treatment should be made for autoantibody-mediated AAE where very high doses can be needed depending on the rate of C1-Inh consumption.

Angioedema↗
PubMed1995

Effect of soluble complement receptor-1 on neutrophil accumulation after traumatic brain injury in rats.

As part of the acute inflammatory response, neutrophils accumulate in the central nervous system after injury. Recently, a soluble human recombinant complement receptor (sCR1; BRL 55730; T Cell Sciences, Inc., Cambridge, MA, U.S.A.) has been developed that inhibits the activation of both the classical and the alternative pathways of complement. sCR1 attenuates the effects of the acute inflammatory response in several models of injury outside the central nervous system. The role of complement in traumatic brain injury, however, remains undefined. We hypothesized that treatment with sCR1 would attenuate neutrophil accumulation in the brain after cerebral trauma. Using a randomized, blinded protocol, 18 anesthetized Sprague-Dawley rats were pre-treated with sCR1 or saline (control) at both 2 h and 2 min before trauma (weight drop) to the exposed right parietal cortex. A third dose of sCR1 (or saline) was given 6 h after trauma. Coronal brain sections centered on the site of trauma were obtained at 24 h after trauma and analyzed for myeloperoxidase (MPO) activity as a marker of neutrophil accumulation. Complete blood counts with differential were obtained before treatment with sCR1 and at 24 h after trauma. At 24 h after trauma, brain MPO activity was reduced by 41% in sCR1-treated rats compared with control rats [0.1599 +/- 0.102 versus 0.2712 +/- 0.178 U/g (mean +/- SD); p = 0.02]. The neutrophil count in peripheral blood increased approximately twofold in both groups. Neutrophil accumulation occurring in the brain after trauma is inhibited by sCR1 treatment. This suggests that complement activation is involved in the local inflammatory response to traumatic brain injury and plays an important role in neutrophil accumulation in the injured brain.

Animals↗
PubMed2001

Validation of an ELISA for the quantitation of human complement receptor 1.

An ELISA was developed and validated for the quantitation of Complement Receptor 1 (CR1) in human plasma. The ELISA employed a monoclonal anti-CR1 antibody adsorbed onto microtiter plates to capture CR1 in human plasma. The captured CR1 was treated with a detecting antibody which had a different epitopic specificity for CR1. HRP conjugated anti IgG (secondary antibody) was used for quantitation. The standard curve covered a wide range from 10 pg to 800 pg. The inter- and intra-assay variation were found to be low and within the acceptable limits. Specificity and accuracy for the assay was established by ensuring negligible cross reactivity with other proteins and an excellent parallelism between the sample and standard curve. The samples were checked for loss of sCR1 levels through freeze/thaw cycles at different intervals of time stored at -70 degrees C.

Complement C1↗
PubMed1985

Binding and activation of human precursor C1 by soluble aggregates of human and rabbit IgG.

The capacities of soluble human and rabbit IgG aggregates to bind and to activate human C1 were compared. Aggregates prepared by incubation of purified IgG at 63 degrees C were fractionated by gel filtration and hemolytic assays were used to measure the binding and activation of isolated human precursor C1. The C1 binding and activation capacities of both human and rabbit IgG aggregates were highly dependent on their size. Human IgG aggregates had a slightly higher binding avidity for human C1 than rabbit IgG aggregates of comparable size, but no clear differences were found between their capacities to activate C1. Experiments with nonaggregated IgG also indicated that although human IgG binds human C1 somewhat more avidly, human and rabbit IgG do not differ in their capacities to initiate fluid-phase activation of the human classical complement pathway.

Animals↗
PubMed1980

Extracts of airborne grain dusts activate alternative and classical complement pathways.

This study investigated the action of aqueous extracts of airborne grain dusts on the human alternative and classical complement pathways. Extracts were shown to consume hemolytic complement in vitro in a dose-dependent manner. No relationship was determined between complement activity ranking and either protein or endotoxin levels. Differential serum chelation with EDTA or EGTA showed that the alternative pathways were activated, while hemolytic titers of the early complement components (C1, C4, C2 and C3) showed that the classical pathway was also involved. Extract-treated sera were chemotactic for human polymorphonuclear leukocytes and complement was required. The in vitro data suggest the potential for the in vivo contribution of the activation of the complement cascade (by either pathway) in eliciting pulmonary pathophysiology after the inhalation of airborne grain dusts.

Chelating Agents↗
PubMedDate not supplied

The value of C1 esterase inhibitor in patients with aspirin-sensitive urticaria.

The aim of the study was to evaluate the concentration and activity of C1 esterase inhibitor (C1 INH) in patients with aspirin-sensitive urticaria. C1 INH deficiency is the basis of hereditary angioneurotic edema. The study was performed on 32 subjects with aspirin-sensitive urticaria. The value of C1 INH in examined patients was the same as in the control group. There seems to be no coexistence of aspirin-sensitive urticaria and C1 esterase inhibitor deficiency.

Adolescent↗
PubMed1986

Dirofilaria immitis: diethylcarbamazine-induced anaphylactoid reactions in infected dogs.

The immunopathogenesis of the anaphylactoid Mazzotti reactions has been studied by comparing physiologic and immunologic aspects of diethylcarbamazine-induced shock in Dirofilaria immitis infected dogs with antigen induced anaphylaxis in infected and uninfected controls. Filarial antigen, specific host IgG antibody, and C1 and C3 complement levels were quantitatively measured over time in relation to the levels of histamine and prostaglandin D2 in the blood and changes in mean blood pressure. D. immitis antigen injected into uninfected dogs having no detectable IgG antibody to D. immitis or Toxocara canis produced a rapid drop in blood pressure that paralleled a drop in C1 and C3 levels and an increase in prostaglandin D2. Antigen injected into infected dogs with IgG antibody produced a similar drop in blood pressure and complement and increase in prostaglandin D2 which differed from the uninfected group only in the slower clearance of antigen from the blood. Diethylcarbamazine alone produced no measurable changes in blood pressure or complement in uninfected hosts. Diethylcarbamazine, however, administered into skin test positive infected dogs, produced a temporally slower but quantitatively similar loss in blood pressure, drop in complement, and increase in prostaglandin D2 and histamine to that induced by antigen injection. Complement activation and immune complex formation are initiated by antigen release, and subsequent vasoactive mediator release leads to shock with prostaglandin D2 being quantitatively higher in blood than is histamine.

Airway Resistance↗
PubMed1993

Assembly of the C1 complex.

The C1 complex of complement is a Ca(2+)-dependent complex protease comprising two loosely interacting subunits. C1q, the recognition subunit, is an hexameric protein with six peripheral globular domains, each connected through collagen-like "arms" to a central fibril-like "stalk". The catalytic subunit, C1s-C1r-C1r-C1s, is a Ca(2+)-dependent tetrameric association of two serine protease zymogens, C1r and C1s, that are sequentially activated by cleavage of a single peptide bond, upon binding of C1 to activators. Each monomeric protease is comprised of six structural motifs which form at least four domains, distributed in two functionally distinct regions, alpha (N-terminal) and gamma-B (C-terminal). The catalytic (gamma-B) regions of C1r and C1s are respectively located in the centre and at each end of the isolated tetramer, and the Ca(2+)-dependent C1r-C1s associations are mediated by the interaction (alpha) regions, which contain one Ca2+ binding site each. Physicochemical and electron microscopy studies indicate that the tetramer, which is highly elongated, folds into a more compact conformation upon interaction with C1q. Various models for C1 have been proposed, in which the tetramer either interacts with the outside part of the C1q arms (O- and W-shaped models), or is folded within the C1q arms (S- or 8-shaped models). These models are discussed in light of available information and in consideration of the structural requirements of C1 activation and function.

Complement C1↗