C3b2-IgG Complexes Retain Dimeric C3 Fragments at All Levels of Inactivation

Jelezarova, Emiliana; Luginbuehl, Alexander; Lutz, Hans

doi:10.1074/jbc.m304613200

Cited by 28 publications

(17 citation statements)

References 47 publications

(36 reference statements)

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“…SPARC (secreted protein acidic and rich in cysteine) (which is secreted by megakaryocytes with a possible role in hematopoiesis (58)) and collagen (binds to CD36 (59) and present both on erythrocytes and platelets) were also identified as was prosaposin (secreted by liver; found in various organs including nervous system (60) and may transfer gangliosides from liposomes to erythrocyte ghost membranes (61)). In contrast to human RBC binding of covalent C3b2-IgG complexes (62,63), in mice elements of the classical complement pathway were evident.…”

Section: Comparative Analysis Of Mouse and Human Rbc Proteomesmentioning

confidence: 99%

Deep Coverage Mouse Red Blood Cell Proteome

Pasini

Kirkegaard

Salerno

et al. 2008

Molecular & Cellular Proteomics

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Mice have close genetic/physiological relationships to humans, breed rapidly, and can be genetically modified, making them the most used mammal in biomedical research. Because the red blood cell (RBC) is the sole gas transporter in vertebrates, diseases of the RBC are frequently severe; much research has therefore focused on RBC and cardiovascular disorders of mouse and humans. RBCs also host malaria parasites. Recently we presented an in-depth proteome for the human RBC. Here we present directly comparable data for the mouse RBC as membrane-only, soluble-only, and combined membranebound/soluble proteomes (comprising, respectively, 247, 232, and 165 proteins). All proteins were identified, validated, and categorized in terms of subcellular localization, protein family, and function, and in comparison with the human RBC, were classified as orthologs, family-related, or unique. Splice isoforms were identified, and polypeptides migrating with anomalous apparent molecular weights were grouped into putatively ubiquitinated or partially degraded complexes. Overall there was close concordance between mouse and human proteomes, confirming the unexpected RBC complexity. Several novel findings in the human proteome have been confirmed here. This comparison sheds light on several open issues in RBC biology and provides a departure point for more comprehensive understanding of RBC function.

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Section: Comparative Analysis Of Mouse and Human Rbc Proteomesmentioning

confidence: 99%

Deep Coverage Mouse Red Blood Cell Proteome

Pasini

Kirkegaard

Salerno

et al. 2008

Molecular & Cellular Proteomics

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“…Either the gels were stained, dried, and exposed to PhosphorImager screens (Molecular Dynamics) for autoradiography or the polypeptides were blotted onto Immobilon P (Millipore, Bedford, MA). Blots were incubated with 0.5% rabbit antiserum against an acidic terminal segment of PfEMP1 (14) and then with 125 I-labeled protein G as outlined previously (22). Monomeric IgG was isolated from Sandoglobulin (ZLB Behring, Berne, Switzerland) by gel filtration in PBS (pH 7.4) on a Sephacryl S300 column (2.5 by 80 cm; Amersham, Little Chalfont, England).…”

Section: Methodsmentioning

confidence: 99%

Complement Factor D, Albumin, and Immunoglobulin G Anti-Band 3 Protein Antibodies Mimic Serum in Promoting Rosetting of Malaria-Infected Red Blood Cells

et al. 2007

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Rosetting of Plasmodium falciparum-infected red blood cells (parasitized RBC [pRBC]) with uninfected RBC has been associated in many studies with malaria morbidity and is one form of cytoadherence observed with malarial parasites. Rosetting is serum dependent for many isolates of P. falciparum, including the strains FCR3S1.2 and Malayan Camp studied here. We identified the three naturally occurring components of sera which confer rosetting. Complement factor D alone induced 30 to 40% of de novo rosetting. Its effect was additive to that of 0.5 mg/ml albumin and to that of 15 ng/ml of naturally occurring antibodies to the anion transport protein, band 3. The three components together mediated rosetting as effectively as 10% serum. De novo rosetting experiments showed that naturally occurring anti-band 3 antibodies as well as factor D were effective only when added to pRBC. Factor D appeared to cleave a small fraction of a protein expressed on the surface of pRBC.Cerebral malaria occurs from infections with Plasmodium falciparum, the parasite species that shows sequestration in the periphery. Sequestration is a means by which parasitized red blood cells (pRBC) escape from their clearance from the reticuloendothelial system. It is mediated by cytoadherence and rosetting of pRBC with uninfected RBC. Clinical studies and autopsies have indeed revealed rosettes in blood vessels from malaria victims (19,20,40,43), and parasites isolated from patients with severe disease formed more and larger rosettes than those from uncomplicated cases (4, 47). For many parasite isolates, in vitro rosetting is dependent on serum factors that are also present in nonimmune, healthy persons. Thus, it is more than a coincidence that the mortality from cerebral malaria is highest in very young children, who have not developed immunity against the parasite but have partially established their innate immune systems. The serum factors that have been shown to mediate rosetting are immunoglobulins (15,43,45), albumin (48), and a third so far unidentified small component which does not bind to concanavalin A (45). We embarked on a study of these serum factors in more detail because neither the specificities of the involved innate immunoglobulins (naturally occurring antibodies [NAbs]) nor the role of complement has been investigated. . When the parasitemia reached 5 to 10%, the culture was diluted to achieve 0.2 to 0.5% parasitemia and culture was continued. Twice a month, cultured parasites were enriched for the rosetting phenotype (49). MATERIALS AND METHODSRosette disruption. A rosetting parasite culture containing P. falciparum late stages at a parasitemia of 5 to 10% was centrifuged for 5 min at 500 ϫ g. Cells were washed twice with phosphate-buffered saline (PBS)-glucose (pH 7.4) and resuspended to a 20% hematocrit in PBS-glucose containing 5 mM sodium citrate, and rosettes were disrupted by passing the resuspended cells 20 times through a 23-gauge 0.6-mm-diameter needle. Cells were then washed once with PBS-glucose containing 5 mM sodium ...

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“…14 The second most abundant complex represents C3b 2 and appears as a band composed of 2 ␣ЈC3b subunits (complex b). 31 Both complexes were almost fully cleavable by hydroxylamine and released ␣ЈC3b (Figure 1). Among the minor, yet uncharacterized complexes with MW exceeding that of complex a, none contained significant amounts of IgG (not shown).…”

Section: Assessment Of C3b-containing Complexes In Human Plasmamentioning

confidence: 99%

Intravenously applied IgG stimulates complement attenuation in a complement-dependent autoimmune disease at the amplifying C3 convertase level

Lutz

Stammler

Bianchi

et al. 2004

Blood

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Intravenously applied normal human immunoglobulin G (IgG) has anti-inflammatory effects in the treatment of autoimmune diseases. Systemic inflammation can originate from an overreacting amplification loop of the complement system. In blood, C3b 2 -containing complexes maintain complement amplification much better than the extremely short-lived C3b. Therefore, in patients with the complement-dependent autoimmune disease, dermatomyositis, we studied whether intravenously applied normal human IgG (IVIG) stimulated in vivo inactivation of these complexes. In the course of IVIG treatment, clinically effective in 6 of 8 patients, the concentration of C3b 2 -containing complexes dropped to 37% ؎ 14% (n ‫؍‬ 6) of the pretreatment level when having infused 0.5 g IgG/kg body weight, increased marginally and in parallel to factor Bb thereafter until full-dose IgG was infused. By day 14 following infusion of 2 g IgG/kg body weight the concentration of C3b 2 -containing complexes was 66% ؎ 19%. The plasma concentration of C3 remained constant in myopathic or increased by 15% to 20% in amyopathic patients. In contrast to this, IVIG infusion was associated with consumption of up to 40% of plasma C4 at day 1 to 2 after completion of IVIG infusion. Thus, IVIG had an immediate and long-lasting attenuating effect on complement amplification in vivo, despite the fact that it induced classical complement pathway activation. IntroductionIntravenously applied human immunoglobulin G (IgG) has an immunomodulatory potential. 1 This effect might in part be due to modulation of phagocytic cells either by altering autocrine or paracrine cytokines through the action of anticytokine antibodies 2,3 or alterations of cell receptor functions 4 or expression. 5,6 Intravenously applied human IgG (IVIG) is, however, similarly beneficial in autoimmune diseases that are associated with excessive complement activation via the classical pathway and the amplification loop. [7][8][9] Such complement activation is proinflammatory by generating C3b in excess. C3b, the active form of C3, binds covalently to targets and promotes generation of C3 convertases, which, in turn, consume C3 and allow assembly of C5 convertase. Elevated C3/C5 convertase activity 10 produces locally proinflammatory anaphylatoxins, C3a/C5a, and generates C5b that can initiate formation of the membrane attack complex on target cells. Finally, insertion of C5b to 7 and C9 into membranes of nucleated cells can result in activation of the arachidonic acid pathway that forms mediators of inflammation. 11 IVIG at high doses is able to displace nascent C3b from tissue-bound immune complexes to the fluid phase 12,13 by serving as a preferential binding site for C3b. 14 Although this process reduces local complement activation, it does not stop systemic complement amplification. Indeed, nascent C3b deposited to fluid-phase IgG primarily forms C3b 2 -IgG complexes. 14 These complexes represent potent activators of the amplification loop and are, on a molar basis, more efficient activators tha...

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C3b2-IgG Complexes Retain Dimeric C3 Fragments at All Levels of Inactivation

Cited by 28 publications

References 47 publications

Deep Coverage Mouse Red Blood Cell Proteome

Deep Coverage Mouse Red Blood Cell Proteome

Complement Factor D, Albumin, and Immunoglobulin G Anti-Band 3 Protein Antibodies Mimic Serum in Promoting Rosetting of Malaria-Infected Red Blood Cells

Intravenously applied IgG stimulates complement attenuation in a complement-dependent autoimmune disease at the amplifying C3 convertase level

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