Complement evasion by protozoa.
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Fresh isolated blood cells recombined with normal heparinized plasma and then incubated with endotoxin, induced a 100-fold increase in monocyte tissue thromboplastin synthesis. In contrast, recombination of these cells with heat inactivated plasma, cobra venom factor-treated plasma, Ca2+-free plasma, or BioRex 70-treated plasma (plasma free of Clq and D) before incubation with endotoxin, failed to induce monocyte synthesis of tissue thromboplastin. These results strongly support the hypothesis that complement is required for endotoxin stimulation of blood monocyte synthesis of tissue thromboplastin.
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We have examined the possible relationship between trichomonad killing by human serum and the presence of virus-encoded double-stranded ribonucleic acid in T. vaginalis (TVV). Indirect immunofluorescence assay revealed that non-immune serum (NIS) and T. vaginalis-immune serum (TVIS) had immunoglobulin G (IgG) antibody titres of 1:8 and 1:256, respectively, against T. vaginalis. Among the 12 isolates of T. vaginalis examined, 9 were infected with TVV. Upon long-term (> 9 months) culture, of the 9 infected isolates, 3 isolates lost the virus during the passage process. Five of 9 TVV-infected isolates were completely killed by 10% NIS while the other 4 TVV-infected isolates had viability over the range 22-81%. Three fresh non-TVV-infected isolates had viability over the range 12-89%. On the other hand, no trichomonads survived in the presence of 10% TVIS. Viability of the virus-lost isolates during long-term culture was not altered when compared with that of their corresponding fresh isolates. Heat-inactivated-NIS and -TVIS had no killing effect on trichomonads while absorbed-NIS and -TVIS (ATVIS) had a similar killing effect to NIS. Further studies on the role of antibody and complement in the killing of trichomonads by serum revealed no significant difference in trichomonad viability between treatments of Mg2+-ethylene glycol-bis-(beta-aminoethyl ether)- N,N,N1,N1- tetraacetic acid (Mg(2+)-EGTA)-TVIS and of Mg(2+)-EGTA-ATVIS. Zymosan-treated ATVIS did not kill trichomonads but zymosan-treated TVIS had a marked killing effect.(ABSTRACT TRUNCATED AT 250 WORDS)
A simple electrophoretic technique employing commercially available agarose films is described for the routine estimation of plasma complement C3 conversion. This technique has particular value in the investigation of anaphylactoid responses in patients following the administration of intravenous hypnotic drugs, plasma substitutes or radio-contrast media.
A sensitive colorimetric microassay for determining haemolytic complement activity was devised. It is carried out in U-welled microtitre dishes covered with plastic tape, which are incubated in a waterbath and subsequently centrifuged. The supernatant is transferred to flat-bottomed microtitre dishes and haemolysis is estimated by automatic measuring of the absorption using an interference filter of 405 nm in a Titertek Multiskan. Advantages of the method described are saving time and materials, and avoiding the use of radioactive nuclides. This microassay may therefore be a useful substitute for macro and semi-micro tests for colorimetric determination of serum complement activity and for microassays based on the release of a radio-isotope.
Neither Naegleria nor its culture supernatant was found to be directly chemotactic for human neutrophils. Interaction of Naegleria with human serum, however, resulted in the generation of a strong chemotactic stimulus. The reduction of serum activity by heat-inactivation indicated a dependence on serum complement for the interaction. The ability of Naegleria to activate the alternative complement pathway was demonstrated with the use of C2-deficient serum.
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Explore the source record for details and available documents.
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The interaction between blood and the artificial devices used in haemodialysis results in the activation of the immune system. Complement activation is known to play a key role in the production of inflammatory mediators. This article describes the complement system and the way in which it is triggered in the patient undergoing haemodialysis. It highlights those factors thought to be of particular importance in the pathogenesis of adverse reactions and targets them as obstacles to be overcome in the future design of biocompatible materials.
The present study was undertaken to determine whether teicoplanin and vancomycin influence the hemolytic and bactericidal activity of serum obtained from mice (Swiss, aged 15 +/- 2 weeks). Haemolytic activity was measured in CH-50 units (which represents the capacity of serum complement to lyse 50% of sheep red blood cells in the presence of specific antibody) and the bactericidal activity was estimated from the number of colony-forming units (CFU/ml) of Staphylococcus aureus that survived after 24 h of incubation in the presence of serum. The results indicate that (1) teicoplanin and vancomycin increase the haemolytic activity of serum; (2) in the serum from animals treated with both teicoplanin or vancomycin, the number of CFU/ml of Staphylococcus aureus declines; and (3) these antibiotics appear to have a similar effect upon the complement system.
The immediate barrier to xenotransplantation across phylogenetically distant species, a manifestation of natural immunity, is hyperacute rejection of the xenograft. Complement (C) plays a central pathophysiological role in hyperacute rejection. Hyperacute rejection is initiated when C is activated by natural antibodies against the vascular endothelium of the transplanted organ or by the endothelium itself. C activation fragments alone or in conjunction with natural antibodies set in motion a series of events in the vasculature of the xenogeneic organ which result in loss of endothelial functional integrity and fibrin deposition. This article reviews recent findings concerning the role of C in hyperacute rejection and evidence suggesting that inhibition of C activation may be a critical approach to avert hyperacute rejection.
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