Search results for "Complement C3b"

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…

Activation of the alternative pathway of complement: efficient fluid-phase amplification by blockade of the regulatory complement protein β1H through…

1981

Current concepts of activation of the alternative pathway of complement (APC) focus on the central role of an amplification mechanism triggered by C3b which is covalently bound to the surfact of activating substances. Using sulfated polyanions as model substances, an efficient fluid-phase activation of complement is demonstrated in contrast to solid-phase activation. It is shown that particulate high-molecular weight sulfated polyanions are capable of reversible binding the guinea pig and human regulatory protein beta1H. This fixation leads to an extensive activation of C3 and factor B because the regulatory function of beta1H is blocked in the fluid-phase C3b-dependent amplification system…

Cyclic AMP-mediated upregulation of the expression of neuronal NO synthase in human A673 neuroepithelioma cells results in a decrease in the level of…

2004

The expression level of neuronal nitric oxide synthase (nNOS) can vary depending on the (patho)physiological conditions. Here we document a marked induction of nNOS mRNA, protein, and total NO production in response to dibutyryl cyclic AMP (db-cAMP) in human A673 neuroepithelial cells. However, the upregulation of nNOS was associated with a decreased level of production of bioactive NO and by an increase in the level of generation of reactive oxygen species (ROS). ROS production could be prevented by the NOS inhibitor L-NAME, suggesting nNOS itself is involved in ROS generation. Sepiapterin supplementation of db-cAMP-treated A673 cells could restore full bioactive NO production, most likely…

Factors influencing the interaction of herpes simplex virus glycoprotein C with the third component of complement.

1992

The factors influencing the interaction of herpes simplex virus (HSV) glycoprotein C (gC) with the third component of complement (C3) were investigated in this study. The ability of gC of HSV type 1 (gC-1) to bind to the C3b fragment of C3 was found to be influenced by cell specific processing of gC-1 in a different manner, binding being remarkably enhanced in some cell lines following removal of sialic acid residues. Testing several intertypic recombinants of HSV we found that only strains expressing gC-1 exhibited binding to C3b, even though their genome consisted mainly of HSV-2 sequences in some recombinants. Expression of type-2 glycoproteins gB, gD, gE, gG, gH, and gI did not alter th…

Complement components in relation to macrophage function

1983

The Properdin System: Composition and Function

1978

. This article summarizes the physicochemical data on the factors which compose the properdin system in guinea pig and man. The following other topics are discussed: (1) Activation of the properdin system; (2) Formation of the initiating and amplification C3 convertases; (3) Formation of the C5 convertase, and (4) Regulatory control mechanisms of the properdin system.

Suppressive effects of C3b on monocyte-dependent T cell proliferation.

1987

The effect of C3b treatment of human monocytes on secondary antigen-dependent T cell response was studied. When antigen-specific T cell blasts were cultivated together with C3b-treated monocytes the proliferative response was inhibited in a dose-dependent fashion. This suppressive effect was specific for C3b because heat-inactivated C3b or buffer alone had no influence on T cell proliferation. In part, this suppressive effect is mediated through a C3b-induced decreased expression of class II antigens on the surface of treated monocytes, but another suppressive mechanism exists because the C3b pretreatment of monocytes also led to an inhibition of the proliferative response in a class II ant…

Effects of hydrocortisone on binding of IgG or C3b-coated erythrocytes to human monocytes and polymorphonuclear leucocytes.

1979

The apolipoprotein(a) moiety of lipoprotein(a) interacts with the complement activation fragment iC3b but does not functionally affect C3 activation …

1992

A previous study has shown that complement component C3 binds to recombinant apolipoprotein(a) (r-apo(a)). In the present report we have investigated the interactions between lipoprotein(a) (Lp(a)), r-apo(a) and C3 in relation to complement activation and degradation. Neither Lp(a) nor r-apo(a) affected complement activation as indicated by sheep and rabbit red blood cell hemolytic assays, and by assessment of the amount of C3a generated in zymosan-activated human serum in the presence or absence of Lp(a). Crossed immunoelectrophoretic analyses indicated that Lp(a) retarded the migration of iC3b in complement-activated serum but had no effects on C3, C3b, C3c or C3dg. Recombinant apo(a) exh…

Importance of Factors H and I for the Adherence of C3b-Coated Erythrocytes to Cells

1983

Abstract The role of cell membrane-associated human factor H for the binding of cell-bound Cab to complement receptor-carrying (CR + ) cells was investigated. Pretreatment of CR + cells with antibodies to factor H inhibited the adherence of Cab-coated red cells to human tonsil lymphocytes (TL) and peripheral blood monocytes (Mo). The Cab receptor reactivity of human polymorphonuclear leucocytes (PMN) was not influenced and the one of Raji lymphoblastoid cells only slightly influenced; iC3b and Cad receptor reactivity was in no case affected. When diisopropylfluorophosphate (DFP) in a concentration of 0.1 mM was present during pretreatment of the CR + cells with anti H, the antibodies gained…