Activation of human complement by crude and purified antigens from Echinococcus granulosus

Inhibition of the Complement System by Glutathione: Molecular Mechanisms and Potential Therapeutic Implications

Glutathione (GSH), a component of the antioxidant defence system, plays a role in autoimmunity and the complement system is often responsible for tissue damage in autoimmune diseases. The aim of this study is to evaluate the effects of GSH on the complement system. The complement system was examined in the normal human sera (NHS) of 30 healthy subjects. Increasing quantities of GSH (1, 2, 10, 20 mg) were incubated in 1 ml of each NHS. The mixtures were evaluated for complement activities (THC, CPA and APA) and for the presence of cleavage fragments of activation of C3 and B. GSH was also incubated with human complement in the presence of classical and alternative pathway activators. The results showed an inhibitory effect of GSH on the complement system starting from a dosage of GSH≥1 mg/ml. Indeed, when NHS was incubated with GSH at such dosage, a significant reduction of the complement activities THC, CPA, and APA was observed (P<0.0001, P<0.005, P=NS, respectively), and no cleavage fragments of C3 or B were found. Further analysis demonstrated that the inhibition was exerted on C3-9 and to a lower extent on classical and alternative pathway C3-convertases. Our results indicate that GSH is capable of inhibiting the complement system. These findings are relevant for the design of interventions aimed at modulation of GSH metabolism to inhibit complement-mediated damage in autoimmune diseases.

Control of host complement activation by the Echinococcus granulosus hydatid cyst

Cystic hydatid disease is caused by the multicellular parasite Echinococcus granulosus. The hydatid cyst, being a long-lived, large, antigenic structure lodged in the host's internal organs, could potentially elicit major inflammatory responses. However, in practice, the cyst causes only minimal local inflammation. The complement system is a major pathway to immune-mediated inflammation. Recent results have shown that the host-exposed structure of the cyst, the hydatid cyst wall (HCW), fails to trigger the complement system strongly. We have carried out a wide survey for the mechanisms making the cyst wall relatively complement-inert. The results of those studies are summarised in this work, with emphasis on the most recently identified of the complement inhibitory mechanisms. This is based on a non-protein heat-stable, parasite inhibitor of the activation of host complement factor B.

Functionally active complement is present in human ovarian follicular fluid and can be activated by seminal plasma

Human ovarian preovulatory follicular fluids (FF) from 10 women were analysed for their complement contents. Functionally active complement was detected in all the fluids studied in amounts similar to those present in normal human serum. Pooled FF was challenged by seminal plasma in order to determine whether seminal plasma could activate FF complement, the pattern of such an activation and the possible consequences on the reproductive function. FF complement activation occurred during the incubation with seminal plasma with features including alternative pathway activation, factor B and C3 conversion and reduction in total haemolytic complement, as well as an inhibition by seminal plasma of the FF complement response to a new activating challenge. Possible consequences for fertilization, implantation of a fertilized ovum and local defence mechanisms against viruses and bacteria are discussed.

Hereditary angioneurotic edema: clinical and laboratory findings in 58 subjects

An in-depth analysis of clinical and laboratory findings in 58 patients affected by hereditary angioneurotic edema (HANE) is reported with special focus on problems related to the diagnosis of the disorder. The functional C1 inhibitor (C1INH) assay is the method of choice in the diagnosis of HANE, as it is capable of revealing the disorder with 100% accuracy. The immunochemical assay of C1INH detected HANE in 84.5% of the cases, i.e., immunochemical deficiency of C1INH (type I HANE). C4 was markedly reduced in both type I and type II HANE; thus, C4 levels can be particularly useful when C1INH functional tests are not available. CH50 testing is of little diagnostic value since total hemolytic complement activity is reduced in a variety of other congenital or acquired pathologies involving the complement system. The CH50 assay after incubation in low ionic strength buffer may be utilized in mass screening programs for qualitative evaluation. However, the test has the drawback of not being applicable in cases of frank hypocomplmentemia. While a depletion of the complement classical pathway was detected in most cases, no alteration in the complement alternative pathway was recorded, nor there was any reduction in immunoglobulin levels. Family history was positive in 100% of the cases. Attacks were almost always brought on by stress and/or trauma, though the causes were sometimes unknown. Edema could be cutaneous (non-pitting and non-pruritic) in 94.2%, laryngeal (often life-threatening) in 48% and abdominal (almost always painful) in 88.4% of patients. Associated pathologies were found in 2 patients, i.e., lupus rash and C3NeF-positive chronic membranoproliferative glomerulonephritis, respectively.