Search results for "Alternative complement pathway"

The Role of the Classical Pathway for the Bactericidal Effect of Normal Sera Against Gram-Negative Bacteria

1985

Many gram-negative bacteria are killed after treatment with normal serum. This phenomenon was already described in 1889 by Buchner. The serum-bactericidal effect is abolished when serum has been incubated for 30 min at 56° C. Gram-positive bacteria are less sensitive than gram-negative bacteria to direct killing, although gram-positive cocci are opsonized by the action of serum mediated by antibodies and complement (Inoue et al. 1968; Johnston et al. 1969). Normal sera exhibit bactericidal and bacteriolytic properties against some gramnegative strains; whereas, other gram-negative strains are serum resistant. It has been shown that serum from C4-deficient guinea pigs is able to kill some gr…

Interaction of Bacterial Endotoxin (LPS) with Fluid Phase and Macrophage Membrane Associated C1q, the FC-Recognizing Component of the Complement Syst…

1990

The bactericidal activity of normal serum was first described by Buchner in 1889 (10). This effect is abolished when serum has been incubated for 30 min at 56°C. Gram positives are less sensitive than Gram negative bacteria to direct killing, although gram positive cocci are opsonized by the action of serum mediated by antibodies and complement (22). It was found that most of the smooth strains of gram negative bacteria are serum resistant; whereas, the corresponding rough forms are extremely serum sensitive (32, 37). Thus evidence was provided that the composition of the bacterial surface may influence the reaction of the bacteria with the lytic system. The bacteriolytic properties of seru…

Complement activation and innate immunity

2007

Combined complete C5 and partial C4 deficiency in humans: clinical consequences and complement-mediated functions in vitro.

1990

A family is described with two siblings who suffered at different times from a single episode of meningococcal meningitis by Neisseria meningitidis groups B and C, respectively. In the two subjects, hemolytically active fifth component of complement (C5) was not detectable and antigenic C5 was less than 0.05% and less than 0.7% of normal, respectively. Repletion of sera by purified human C5 (70 micrograms/ml) restored total complement hemolytic activities. The asymptomatic first degree family members had C5 levels compatible with a heterozygous state of C5 deficiency. C4 allotyping revealed an inherited partial deficiency (Q0) of C4A and C4B in the family with a combined C4AQ0 and C4BQ0 het…

Cloning and expression of the complement receptor glycoprotein C from Herpesvirus simiae (herpes B virus): protection from complement-mediated cell l…

2003

Simian herpes B virus (SHBV) is the herpes simplex virus (HSV) homologue for the species MACACA: Unlike in its natural host, and unlike other animal herpesviruses, SHBV causes high mortality in accidentally infected humans. SHBV-infected cells, like those infected with HSV-1 and equine herpesvirus types 1 and 4, express complement C3 receptor activity. To study immunoregulatory functions involved in susceptibility/resistance against interspecies transmission, the SHBV glycoprotein C (gC(SHBV)) gene (encoding 467 aa) was isolated. Sequence analysis revealed amino acid identity with gC proteins from HSV-2 (46.9 %), HSV-1 (44.5 %) and pseudorabies virus (21.2 %). Highly conserved cysteine resi…

Digestive vacuoles of Plasmodium falciparum are selectively phagocytosed by and impair killing function of polymorphonuclear leukocytes.

2011

AbstractSequestration of parasitized erythrocytes and dysregulation of the coagulation and complement system are hallmarks of severe Plasmodium falciparum malaria. A link between these events emerged through the discovery that the parasite digestive vacuole (DV), which is released together with infective merozoites into the bloodstream, dually activates the intrinsic clotting and alternative complement pathway. Complement attack occurs exclusively on the membrane of the DVs, and the question followed whether DVs might be marked for uptake by polymorphonuclear granulocytes (PMNs). We report that DVs are indeed rapidly phagocytosed by PMNs after schizont rupture in active human serum. Uptake …

Cutting Edge: IL-6–Driven Immune Dysregulation Is Strictly Dependent on IL-6R α-Chain Expression

2020

Abstract IL-6 binds to the IL-6R α-chain (IL-6Rα) and signals via the signal transducer gp130. Recently, IL-6 was found to also bind to the cell surface glycoprotein CD5, which would then engage gp130 in the absence of IL-6Rα. However, the biological relevance of this alternative pathway is under debate. In this study, we developed a mouse model, in which murine IL-6 is overexpressed in a CD11c-Cre–dependent manner. Transgenic mice developed a lethal immune dysregulation syndrome with increased numbers of Ly-6G+ neutrophils and Ly-6Chi monocytes/macrophages. IL-6 overexpression promoted activation of CD4+ T cells while suppressing CD5+ B-1a cell development. However, additional ablation of …

In vitro synthesis of factor B of the alternative pathway of complement activation by mouse peritoneal macrophages

1976

Factor B of the alternative pathway of complement activation was shown to be synthesized and secreted by unstimulated mouse peritoneal macrophages. The activity of B in the culture supernatants from macrophage monolayers was detected by consumption of C3 in reaction mixtures containing supernatant and guinea pig factors C3, D and insoluble C3b. Using a monospecific antiserum, factor B in concentrated culture supernatants was shown by immunodiffusion and immunoelectrophoresis to be identical to factor B in mouse plasma and to form a characteristic complex with cobra venom factor in the presence of D. A steady rate of factor B secretion was observed for 4 days providing the medium was changed…

Digestive vacuole of Plasmodium falciparum released during erythrocyte rupture dually activates complement and coagulation.

2012

Abstract Severe Plasmodium falciparum malaria evolves through the interplay among capillary sequestration of parasitized erythrocytes, deregulated inflammatory responses, and hemostasis dysfunction. After rupture, each parasitized erythrocyte releases not only infective merozoites, but also the digestive vacuole (DV), a membrane-bounded organelle containing the malaria pigment hemozoin. In the present study, we report that the intact organelle, but not isolated hemozoin, dually activates the alternative complement and the intrinsic clotting pathway. Procoagulant activity is destroyed by phospholipase C treatment, indicating a critical role of phospholipid head groups exposed at the DV surfa…

Binding to complement factors and activation of the alternative pathway by Acanthamoeba.

2010

Acanthamoeba can cause severe ocular and cerebral diseases in healthy and immunocompromised individuals, respectively. Activation of complement appears to play an important role in host defence against infection. The exact mechanism, however, is still unclear. The aim of the present study was to investigate the effect of normal human serum (NHS) and normal mouse serum (NMS) on Acanthamoeba trophozoites, the binding of different complement factors to Acanthamoeba and the activation of the complement system. Moreover, we aimed to work out any possible differences between different strains of Acanthamoeba. A virulent T4 strain, a non-virulent T4 strain and a virulent T6 strain were included in…