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Mannose-binding lectin complement pathway plays a key role in complement activation by Paracoccidioides brasiliensis

TOLEDO, Renan G.; SILVA, Wilmar D. Da; CALICH, Vera L. G.; KIPNIS, Thereza L.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
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36.49%
Paracoccidioides brasiliensis (Pb) is a dimorphic fungal pathogen that causes paracoccidioidomycosis the most severe deep mycosis from South America Although cell mediated immunity is considered the most efficient protective mechanism against Pb infection mechanisms of innate immunity are poorly defined Herein we investigated the interaction of the complement system with high and low virulence isolates of Pb We demonstrated that Pb18 a high virulence Pb Isolate when incubated with normal human serum (NHS) induces consumption of hemolytic complement and when immobilized promotes binding of C4b C3b and C5b-C9 Both low virulence (Pb265) and high virulence (Pb18) isolates consumed C4 C3 and mannose-binding learn (MBL) of MBL-sufficient but not of MBL-deficient serum as revealed by deposition of residual C4 C3 and MBL on immune complexes and mannan However higher complement components consumption was observed with Pb265 as compared with Pb18 The suggested relationship between low virulence and significant complement activation properties of Pb isolates was confirmed by the demonstration that virulence attenuation of Pb 18 results in acquisition of the ability to activate complement Conversely reactivation of attenuated Pb18 results in loss of the ability to activate complement Our results demonstrate for the first time that Pb yeasts activate the complement system by the lectin pathway and there is an Inverse correlation between complement activating ability and Pb virulence These differences could exert an influence on Innate immunity and severity of the disease developed by infected hosts (C) 2010 Elsevier Ltd All rights reserved; CNPq; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); FAPERJ; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)

Functional Characterization of LcpA, a Surface-Exposed Protein of Leptospira spp. That Binds the Human Complement Regulator C4BP

BARBOSA, Angela S.; MONARIS, Denize; SILVA, Ludmila B.; MORAIS, Zenaide M.; VASCONCELLOS, Silvio A.; CIANCIARULLO, Aurora M.; ISAAC, Lourdes; ABREU, Patricia A. E.
Fonte: AMER SOC MICROBIOLOGY Publicador: AMER SOC MICROBIOLOGY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.84%
We have previously shown that pathogenic leptospiral strains are able to bind C4b binding protein (C4BP). Surface-bound C4BP retains its cofactor activity, indicating that acquisition of this complement regulator may contribute to leptospiral serum resistance. In the present study, the abilities of seven recombinant putative leptospiral outer membrane proteins to interact with C4BP were evaluated. The protein encoded by LIC11947 interacted with this human complement regulator in a dose-dependent manner. The cofactor activity of C4BP bound to immobilized recombinant LIC11947 (rLIC11947) was confirmed by detecting factor I-mediated cleavage of C4b. rLIC11947 was therefore named LcpA (for leptospiral complement regulator-acquiring protein A). LcpA was shown to be an outer membrane protein by using immunoelectron microscopy, cell surface proteolysis, and Triton X-114 fractionation. The gene coding for LcpA is conserved among pathogenic leptospiral strains. This is the first characterization of a Leptospira surface protein that binds to the human complement regulator C4BP in a manner that allows this important regulator to control complement system activation mediated either by the classical pathway or by the lectin pathway. This newly identified protein may play a role in immune evasion by Leptospira spp. and may therefore represent a target for the development of a human vaccine against leptospirosis.; FAPESP[09/01778-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[06/54701-6]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq[478081/2007-3]; CNPq[564618/2008-0]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Immune Evasion of Leptospira Species by Acquisition of Human Complement Regulator C4BP

BARBOSA, Angela S.; ABREU, Patricia A. E.; VASCONCELLOS, Silvio A.; MORAIS, Zenaide M.; GONCALES, Amane P.; SILVA, Aldacilene S.; DAHA, Mohamed R.; ISAAC, Lourdes
Fonte: AMER SOC MICROBIOLOGY Publicador: AMER SOC MICROBIOLOGY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.68%
Leptospirosis is a spirochetal zoonotic disease of global distribution with a high incidence in tropical regions. In the last 15 years it has been recognized as an important emerging infectious disease due to the occurrence of large outbreaks in warm-climate countries and, occasionally, in temperate regions. Pathogenic leptospires efficiently colonize target organs after penetrating the host. Their invasiveness is attributed to the ability to multiply in blood, adhere to host cells, and penetrate into tissues. Therefore, they must be able to evade the innate host defense. The main purpose of the present study was to evaluate how several Leptospira strains evade the protective function of the complement system. The serum resistance of six Leptospira strains was analyzed. We demonstrate that the pathogenic strain isolated from infected hamsters avoids serum bactericidal activity more efficiently than the culture-attenuated or the nonpathogenic Leptospira strains. Moreover, both the alternative and the classical pathways of complement seem to be responsible for the killing of leptospires. Serum-resistant and serum-intermediate strains are able to bind C4BP, whereas the serum-sensitive strain Patoc I is not. Surface-bound C4BP promotes factor I-mediated cleavage of C4b. Accordingly...

Complement 4 phenotypes and genotypes in Brazilian patients with classical 21-hydroxylase deficiency

GUERRA-JUNIOR, G.; GRUMACH, A. Sevciovic; LEMOS-MARINI, S. H. Valente de; KIRSCHFINK, M.; CONDINO NETO, A.; ARAUJO, M. de; MELLO, M. Palandi De
Fonte: WILEY-BLACKWELL PUBLISHING, INC Publicador: WILEY-BLACKWELL PUBLISHING, INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.25%
The aim of this work was to analyse C4 genotypes, C4 protein levels, phenotypes and genotypes in patients with the classical form of 21-hydroxylase deficiency. Fifty-four patients from 46 families (36 female, 18 male; mean age 10.8 years) with different clinical manifestations (31 salt-wasting; 23 simple-virilizing) were studied. Taq I Southern blotting was used to perform molecular analysis of the C4/CYP21 gene cluster and the genotypes were defined according to gene organization within RCCX modules. Serum C4 isotypes were assayed by enzyme-linked immunosorbent assay. The results revealed 12 different haplotypes of the C4/CYP21 gene cluster. Total functional activity of the classical pathway (CH50) was reduced in individuals carrying different genotypes because of low C4 concentrations (43% of all patients) to complete or partial C4 allotype deficiency. Thirteen of 54 patients presented recurrent infections affecting the respiratory and/or the urinary tracts, none of them with severe infections. Low C4A or C4B correlated well with RCCX monomodular gene organization, but no association between C4 haplotypes and recurrent infections or autoimmunity was observed. Considering this redundant gene cluster, C4 seems to be a well-protected gene segment along the evolutionary process.; FAPESP[92/03332-6]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[97/07622-2]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq[300357/01-0]; CNPq[302334/03-3]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); FAEP-UNICAMP[0863/98]; Universidade Estadual de Campinas (UNICAMP); FAEP-UNICAMP[022/96]; Universidade Estadual de Campinas (UNICAMP)

Leptospiral Immunoglobulin-like Proteins Interact With Human Complement Regulators Factor H, FHL-1, FHR-1, and C4BP

Castiblanco-Valencia, Monica Marcela; Fraga, Tatiana Rodrigues; da Silva, Ludmila Bezerra; Monaris, Denize; Estima Abreu, Patricia Antonia; Strobel, Stefanie; Jozsi, Mihaly; Isaac, Lourdes; Barbosa, Angela Silva
Fonte: OXFORD UNIV PRESS INC; CARY Publicador: OXFORD UNIV PRESS INC; CARY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.74%
Leptospira, the causative agent of leptospirosis, interacts with several host molecules, including extracellular matrix components, coagulation cascade proteins, and human complement regulators. Here we demonstrate that acquisition of factor H (FH) on the Leptospira surface is crucial for bacterial survival in the serum and that these spirochetes, besides interacting with FH, FH related-1, and C4b binding protein (C4BP), also acquire FH like-1 from human serum. We also demonstrate that binding to these complement regulators is mediated by leptospiral immunoglobulin-like (Lig) proteins, previously shown to interact with fibronectin, laminin, collagen, elastin, tropoelastin, and fibrinogen. Factor H binds to Lig proteins via short consensus repeat domains 5 and 20. Competition assays suggest that FH and C4BP have distinct binding sites on Lig proteins. Moreover, FH and C4BP bound to immobilized Ligs display cofactor activity, mediating C3b and C4b degradation by factor I. In conclusion, Lig proteins are multifunctional molecules, contributing to leptospiral adhesion and immune evasion.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo [2010/50043-0]; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo

Caracterização molecular dos componentes C1q, C4 e C2 do sistema complemento em pacientes pediátricos com lúpus eritematoso sistêmico; Molecular characterization of complement components C1q, C4, and C2 in pediatric patients with Systemic Lupus Erythematosus

Umetsu Sobrinho, Natália
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 08/08/2013 PT
Relevância na Pesquisa
37%
Objetivo: Realizar a caracterização molecular dos genes C1q, C4 e C2 em pacientes com lúpus eritematoso sistêmico juvenil (LESJ). Métodos: Quatro pacientes com LESJ e deficiências de C1q,C4 e/ou C2 foram selecionados. O paciente P1 apresentava níveis séricos indetectáveis de C1q e níveis normais de C3 e C4; paciente P2 níveis baixos de C2 e C4 no soro; P3 apresentava níveis baixos de C2 e normais de C3 e C4 e P4 constantes níveis baixos de C4 e níveis normais de C1q, C2 e C3 no soro. Foram sequenciados os genes C1q e C2. Células mononucleares dos pacientes P1, P3 e P4 e de três indivíduos saudáveis foram cultivadas, estimuladas com interferon gama e incubadas por 36 horas e PCR quantitativo (qRTPCR) foi realizado para verificar a expressão de mRNA. Resultados: A caracterização molecular do gene C1q (P1) mostrou trocas heterozigotas na cadeia A (c.276 A>G Gly) e na cadeia C (c.126 C>T Pro). Foram observadas também duas trocas de base em homozigose na região 5'UTR (c. -159 T>G) e na região 3'UTR (c*78 A>G) da cadeia B. O qRT-PCR mostrou que a expressão de mRNA de C1qA no paciente P1 sem estimulo estava 1,3 vezes mais baixo e com estímulo de interferon gama estava 1,6 vezes mais expresso se comparado aos indivíduos saudáveis. A expressão de mRNA de C1qB sem estímulo foi 2...

Interação da proteína de superfície LcpA de Leptospira com Fator H, principal regulador solúvel da via alternativa do sistema complemento humano; Interaction of the surface protein LcpA from Leptospira with Factor H, the main soluble regulator of the alternative pathway of human complement system

Silva, Ludmila Bezerra da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 03/07/2013 PT
Relevância na Pesquisa
36.93%
A leptospirose é uma zoonose de distribuição mundial, com maior incidência nas regiões tropicais. As bactérias que causam a doença pertencem ao gênero Leptospira, família Leptospiracea e ordem Spirochaetales. A leptospirose é mantida na natureza pela colonização persistente dos túbulos renais proximais dos animais portadores. Uma estratégia adotada por estas espiroquetas para sobreviver à ação do sistema imune inato do hospedeiro é a capacidade que possuem de interagir com os reguladores do sistema complemento Fator H (FH) e proteína de ligação a C4b (C4BP). O sistema complemento é um componente vital da imunidade inata, uma vez que desempenha um papel crucial na defesa do hospedeiro, particularmente contra bactérias Gram-negativas. Dados recentes gerados por nosso grupo mostraram que C4BP interage com a proteína de superfície LcpA de Leptospira. Com cerca de 20 kDa, essa proteína é capaz de se ligar a C4BP purificado ou solúvel no soro de maneira dose-dependente. Uma vez ligado à proteína, C4BP permanece funcional agindo como cofator de Fator I na clivagem de C4b. O presente estudo teve como principal objetivo avaliar a interação da proteína LcpA com FH humano, principal regulador solúvel da via alternativa do sistema complemento. A proteína LcpA e suas porções N-Terminal...

Identificação de proteases de Leptospira envolvidas com mecanismos de escape do sistema complemento humano.; Identification of leptospiral proteases involved in immune evasion mechanisms from the human complement system.

Fraga, Tatiana Rodrigues
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 01/08/2014 PT
Relevância na Pesquisa
36.7%
A leptospirose é uma zoonose causada por leptospiras patogênicas. Para estabelecer a infecção, estas bactérias desenvolveram estratégias de escape ao sistema complemento. Neste trabalho demonstramos que o sobrenadante de cultura de leptospiras patogênicas é capaz de inibir as três vias do complemento. Observamos que esse sobrenadante possui atividade proteolítica sobre C3, C3b e iC3b, além do FB (via alternativa), C2 e C4b (via clássica e das lectinas). As proteínas C3, C4, C2 e FB também foram clivadas quando soro humano normal (SHN) foi utilizado como fonte de complemento. Demonstramos que as proteases atuam em conjunto com os reguladores do hospedeiro Fator I e Fator H na clivagem de C3b. As clivagens foram inibidas pela 1,10-fenantrolina, sugerindo a participação de metaloproteases. Metaloproteases de leptospira da família das termolisinas foram produzidas como proteínas recombinantes e clivaram C3 no SHN. Concluímos que proteases de leptospiras patogênicas podem desativar moléculas do complemento e são potencias alvos para novas terapias em leptospirose.; Leptospirosis is a zoonotic disease caused by pathogenic Leptospira. To establish the infection, these bacteria have developed strategies to escape the complement system. In this work...

Interação de proteínas de membrana de Leptospira com os reguladores Fator H e C4BP do sistema complemento humano.; Interaction of Leptospira membrane proteins with human complement regulators Factor H and C4BP.

Valencia, Mónica Marcela Castiblanco
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/09/2014 PT
Relevância na Pesquisa
36.68%
Diferentes mecanismos têm sido mostrados por estar envolvidos na evasão à morte mediada por complemento. Neste estudo, demonstramos que a aquisição do FH pela Leptospira é crucial para a sobrevivência das bactérias no soro e que estas espiroquetas interagem com FH, FHL-1, FHR-1 e C4BP. Nós também demonstramos que a ligação à estes reguladores é mediada pelas proteínas leptospiral immunoglobulin-like (Lig). FH se liga as proteínas Lig via short consensus repeat (SCR) principalmente pelos domínios 5 e 20. Ensaios de competição sugerem que FH e C4BP têm sítios de ligação diferentes nas proteínas Lig. Além disso, FH e C4BP ligados nas proteínas Lig mantêm a atividade de cofator, mediando a degradação de C3b e C4b pelo FI. Nós demonstramos que a aquisição de FH e C4BP pela L. biflexa transgênica para LigA e LigB exercem um papel de proteção na sobrevida destas bactérias. Análise por citometria de fluxo também confirmaram a capacidade das leptospiras transgênicas para controlar a deposição de C3, C4 e MAC. As proteínas Lig também foram capazes de ligar plasminogênio, o qual foi ativado em plasmina e esta enzima foi capaz de degradar fibrinogénio, C3b e C5. Estas clivagens inativam C3b e C5, evitando a progressão da cascata...

Complement 4 phenotypes and genotypes in Brazilian patients with classical 21-hydroxylase deficiency

GUERRA-JUNIOR, G.; GRUMACH, A. Sevciovic; LEMOS-MARINI, S. H. Valente de; KIRSCHFINK, M.; CONDINO NETO, A.; ARAUJO, M. de; MELLO, M. Palandi De
Fonte: WILEY-BLACKWELL PUBLISHING, INC Publicador: WILEY-BLACKWELL PUBLISHING, INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.25%
The aim of this work was to analyse C4 genotypes, C4 protein levels, phenotypes and genotypes in patients with the classical form of 21-hydroxylase deficiency. Fifty-four patients from 46 families (36 female, 18 male; mean age 10.8 years) with different clinical manifestations (31 salt-wasting; 23 simple-virilizing) were studied. Taq I Southern blotting was used to perform molecular analysis of the C4/CYP21 gene cluster and the genotypes were defined according to gene organization within RCCX modules. Serum C4 isotypes were assayed by enzyme-linked immunosorbent assay. The results revealed 12 different haplotypes of the C4/CYP21 gene cluster. Total functional activity of the classical pathway (CH50) was reduced in individuals carrying different genotypes because of low C4 concentrations (43% of all patients) to complete or partial C4 allotype deficiency. Thirteen of 54 patients presented recurrent infections affecting the respiratory and/or the urinary tracts, none of them with severe infections. Low C4A or C4B correlated well with RCCX monomodular gene organization, but no association between C4 haplotypes and recurrent infections or autoimmunity was observed. Considering this redundant gene cluster, C4 seems to be a well-protected gene segment along the evolutionary process.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Molecular characterization of the complement C1q, C2 and C4 genes in Brazilian patients with juvenile systemic lupus erythematosus

Liphaus,Bernadete L.; Umetsu,Natalia; Jesus,Adriana A.; Bando,Silvia Y.; Silva,Clovis A.; Carneiro-Sampaio,Magda
Fonte: Faculdade de Medicina / USP Publicador: Faculdade de Medicina / USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2015 EN
Relevância na Pesquisa
36.52%
OBJECTIVE: To perform a molecular characterization of the C1q, C2 and C4 genes in patients with juvenile systemic lupus erythematosus. METHODS: Patient 1 (P1) had undetectable C1q, patient 2 (P2) and patient 3 (P3) had decreased C2 and patient 4 (P4) had decreased C4 levels. All exons and non-coding regions of the C1q and C2 genes were sequenced. Mononuclear cells were cultured and stimulated with interferon gamma to evaluate C1q, C2 and C4 mRNA expression by quantitative real-time polymerase chain reaction. RESULTS: C1q sequencing revealed heterozygous silent mutations in the A (c.276 A>G Gly) and C (c.126 C>T Pro) chains, as well as a homozygous single-base change in the 3′ non-coding region of the B chain (c*78 A>G). C1qA mRNA expression without interferon was decreased compared with that of healthy controls (p<0.05) and was decreased after stimulation compared with that of non-treated cells. C1qB mRNA expression was decreased compared with that of controls and did not change with stimulation. C1qC mRNA expression was increased compared with that of controls and was even higher after stimulation. P2 and P3 had Type I C2 deficiency (heterozygous 28 bp deletion at exon 6). The C2 mRNA expression in P3 was 23 times lower compared with that of controls and did not change after stimulation. The C4B mRNA expression of P4 was decreased compared with that of controls and increased after stimulation. CONCLUSIONS: Silent mutations and single-base changes in the 3′ non-coding regions may modify mRNA transcription and C1q production. Type I C2 deficiency should be evaluated in JSLE patients with decreased C2 serum levels. Further studies are needed to clarify the role of decreased C4B mRNA expression in JSLE pathogenesis.

Substitution of a single amino acid (aspartic acid for histidine) converts the functional activity of human complement C4B to C4A.

Carroll, M C; Fathallah, D M; Bergamaschini, L; Alicot, E M; Isenman, D E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1990 EN
Relevância na Pesquisa
36.82%
The C4B isotype of the fourth component of human complement (C4) displays 3- to 4-fold greater hemolytic activity than does its other isotype C4A. This correlates with differences in their covalent binding efficiencies to erythrocytes coated with antibody and complement C1. C4A binds to a greater extent when C1 is on IgG immune aggregates. The differences in covalent binding properties correlate only with amino acid changes between residues 1101 and 1106 (pro-C4 numbering)--namely, Pro-1101, Cys-1102, Leu-1105, and Asp-1106 in C4A and Leu-1101, Ser-1102, Ile-1105, and His-1106 in C4B, which are located in the C4d region of the alpha chain. To more precisely identify the residues that are important for the functional differences, C4A-C4B hybrid proteins were constructed by using recombinant DNA techniques. Comparison of these by hemolytic assay and binding to IgG aggregates showed that the single substitution of aspartic acid for histidine at position 1106 largely accounted for the change in functional activity and nature of the chemical bond formed (ester vs. amide). Surprisingly, substitution of a neutral residue, alanine, for histidine at position 1106 resulted in an increase in binding to immune aggregates without subsequent reduction in the hemolytic activity. This result strongly suggests that position 1106 is not "catalytic" as previously proposed but interacts sterically/electrostatically with potential acceptor sites and serves to "select" binding sites on potential acceptor molecules.

Kinetic Analysis of the Interactions between Vaccinia Virus Complement Control Protein and Human Complement Proteins C3b and C4b

Bernet, John; Mullick, Jayati; Panse, Yogesh; Parab, Pradeep B.; Sahu, Arvind
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2004 EN
Relevância na Pesquisa
27.12%
The vaccinia virus complement control protein (VCP) is an immune evasion protein of vaccinia virus. Previously, VCP has been shown to bind and support inactivation of host complement proteins C3b and C4b and to protect the vaccinia virions from antibody-dependent complement-enhanced neutralization. However, the molecular mechanisms involved in the interaction of VCP with its target proteins C3b and C4b have not yet been elucidated. We have utilized surface plasmon resonance technology to study the interaction of VCP with C3b and C4b. We measured the kinetics of binding of the viral protein to its target proteins and compared it with human complement regulators factor H and sCR1, assessed the influence of immobilization of ligand on the binding kinetics, examined the effect of ionic contacts on these interactions, and sublocalized the binding site on C3b and C4b. Our results indicate that (i) the orientation of the ligand is important for accurate determination of the binding constants, as well as the mechanism of binding; (ii) in contrast to factor H and sCR1, the binding of VCP to C3b and C4b follows a simple 1:1 binding model and does not involve multiple-site interactions as predicted earlier; (iii) VCP has a 4.6-fold higher affinity for C4b than that for C3b...

Complement-coated antibody-transfer (CCAT); serum IgA1 antibodies intercept and transport C4 and C3 fragments and preserve IgG1 deployment (PGD)†

Boackle, Robert J.; Nguyen, Quang L.; Leite, Renata S.; Yang, Xiaofeng; Vesely, Jana
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.12%
In periodontal disease, IgG1 and IgA1 antibodies produced in situ deposit on antigens in the affected tissues. Thus, there is an interest in the effect of co-deposited IgA1 antibodies on complement activation by IgG1-immune complexes. In the present study, we first analyzed the effect of IgA1-immune complexes on complement using human IgA1 antibodies to dansyl (with dansylated human serum albumin serving as the immobilized antigen). It was observed that these IgA1-immune complexes when incubated for prolonged times with 33% human serum as a source of complement received C4b and C3b deposition. As C4b and C3b deposited on the IgA1 antibodies and on the antigenic surface, the complement-coated IgA1 antibodies departed. These fluid-phase complement-coated IgA1 antibodies were transferred to antigen-coated microtiter-ELISA plates, where they became bound to the antigens. Thus, the complement-coated IgA1 antibodies retained their antigen-binding function, especially as a proportion of their covalently bound C3b progressively degraded to iC3b and C3d. Genetically engineered carbohydrate-deficient mutant human IgA1 antibodies were used to assess the role of carbohydrate in accepting the C4b and C3b depositions, and these studies indicated that the carbohydrate on the Fc-region of IgA1 played a positive role. Another interesting finding generated by this study was that when IgA1 was co-deposited with IgG1 antibodies...

Increased frequency of the null allele at the complement C4b locus in autism.

Warren, R P; Singh, V K; Cole, P; Odell, J D; Pingree, C B; Warren, W L; White, E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1991 EN
Relevância na Pesquisa
36.65%
Associations between C4 deficiency and autoimmune disorders have been found over the past several years. Since autism has several autoimmune features, the frequencies of null (no protein produced) alleles at the C4A and C4B loci were studied in 19 subjects with autism and their family members. The autistic subjects and their mothers had significantly increased phenotypic frequencies of the C4B null allele (58% in both the autistic subjects and mothers, compared with 27% in control subjects). The siblings of the autistic subjects also had an increased frequency of the C4B null allele, but this increase was not significant. The fathers had normal frequencies of this null allele. All family members had normal frequencies of the C4A null allele, all normal C4A and C4B alleles and all BF and C2 alleles.

Membrane-bound C4b interacts endogenously with complement receptor CR1 of human red cells

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/11/1986 EN
Relevância na Pesquisa
27.14%
Activation of the classical complement pathway on the membrane of autologous cells results in the deposition of C4b on their surface and in the assembly of the C3 convertase C4b2a, one of the amplifying enzymes of the cascade. Here we study the sequence of events leading to irreversible inactivation of the potentially harmful C4b bound to human red cells. We show that deposited C4b interacts endogenously with complement receptor type 1 (CR1) present on the membrane of the same red cell. Complexes containing CR1 and C4b are found in extracts of membranes of C4b-bearing red cells after treatment of the intact cells with a bifunctional crosslinking reagent. The amount of complexed CR1 increases with the number of deposited C4b molecules. Only small amounts of free CR1 are observed on red cells bearing as few as 1,900 molecules of C4b, suggesting that the binding avidity between C4b and endogenous CR1 is high. In agreement with this observation, we find that the deposited C4b inhibits the exogenous cofactor activity of the red cell CR1 for the factor I-mediated cleavage of target-bound clustered C3b. The C4b bound to the human red cells is cleaved by the serum enzyme C3b/C4b inactivator (factor I) and a large fragment (C4c) is released in the incubation medium. The cleavage is totally inhibited by mAbs against CR1...

Defining Targets for Complement Components C4b and C3b on the Pathogenic Neisseriae▿ †

Lewis, Lisa A.; Ram, Sanjay; Prasad, Alpana; Gulati, Sunita; Getzlaff, Silke; Blom, Anna M.; Vogel, Ulrich; Rice, Peter A.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
37.03%
Complement is a key arm of the innate immune defenses against the pathogenic neisseriae. We previously identified lipooligosaccharide on Neisseria meningitidis as an acceptor for complement C4b. Little is known about other neisserial targets for complement proteins C3 and C4, which covalently attach to bacterial surfaces and initiate opsonization and killing. In this study we demonstrate that Neisseria gonorrhoeae porin (Por) 1B selectively binds C4b via amide linkages and C3b via ester linkages. Using strains expressing hybrid Por1A/1B molecules, a region spanned by loops 4 and 5 of Por1B was identified as the preferred binding site for C4b. We also identified the opacity protein (Opa), a major adhesin of pathogenic neisseriae, as a target for C4b and C3b on both N. meningitidis and N. gonorrhoeae. Using N. gonorrhoeae variants that predominantly expressed individual Opa proteins, we found that all Opa proteins tested (A, B, C, D, E, F, and I) bound C4b and C3b via amide and ester linkages, respectively. Amide linkages with Por1B and Opa were confirmed using serum containing only the C4A isoform, which exclusively forms amide linkages with targets. While monomers and heterodimers of C4Ab were detected on bacterial targets, C4Bb appeared to preferentially participate in heterodimer (C5 convertase) formation. Our data provide another explanation for the enhanced serum sensitivity of Por1B-bearing gonococci. The binding of C3b and C4b to Opa provides a rationale for the recovery of predominantly “transparent” (Opa-negative) neisserial isolates from persons with invasive disease...

Familial C4B Deficiency and Immune Complex Glomerulonephritis

Soto, K; Wu, YL; Ortiz, A; Aparício, SR; Yu, CY
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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36.88%
Homozygous complement C4B deficiency is described in a Southern European young female patient with Membranoproliferative Glomerulonephritis (MPGN) type III characterized by renal biopsies with strong complement C4 and IgG deposits. Low C4 levels were independent of clinical evolution or type of immunosuppression and were found in three other family members without renal disease or infections. HLA typing revealed that the patient has homozygous A*02, Cw*06, B*50 at the class I region, and DRB1*08 and DQB1*03 at the class II region. Genotypic and phenotypic studies demonstrated that the patient has homozygous monomodular RCCX in the HLA class III region, with single long C4A genes coding for C4A3 and complete C4B deficiency. Her father, mother, son and niece have heterozygous C4B deficiency. The patient’s deceased brother had a history of Henoch-Schönlein Purpura (HSP), an immune complex-mediated proliferative glomerulonephritis. These findings challenge the putative pathophysiological roles of C4A and C4B and underscore the need to perform functional assays, C4 allotyping and genotyping on patients with persistently low serum levels of a classical pathway complement component and glomerulopathy associated with immune deposits.

Familial C4B deficiency and immune complex glomerulonephritis

Soto, K; Wu, Y; Ortiz, A; Aparício, S; Yu, C
Fonte: Academic Press Publicador: Academic Press
Tipo: Artigo de Revista Científica
Publicado em //2010 ENG
Relevância na Pesquisa
57%
Homozygous complement C4B deficiency is described in a Southern European young female patient with Membranoproliferative Glomerulonephritis (MPGN) type III characterized by renal biopsies with strong complement C4 and IgG deposits. Low C4 levels were independent of clinical evolution or type of immunosuppression and were found in three other family members without renal disease or infections. HLA typing revealed that the patient has homozygous A*02, Cw*06, B*50 at the class I region, and DRB1*08 and DQB1*03 at the class II region. Genotypic and phenotypic studies demonstrated that the patient has homozygous monomodular RCCX in the HLA class III region, with single long C4A genes coding for C4A3 and complete C4B deficiency. Her father, mother, son and niece have heterozygous C4B deficiency. The patient's deceased brother had a history of Henoch-Schönlein Purpura (HSP), an immune complex-mediated proliferative glomerulonephritis. These findings challenge the putative pathophysiological roles of C4A and C4B and underscore the need to perform functional assays, C4 allotyping and genotyping on patients with persistently low serum levels of a classical pathway complement component and glomerulopathy associated with immune deposits.

Human genes for the alpha and beta chains of complement C4b-binding protein are closely linked in a head-to-tail arrangement.

Pardo-Manuel, F; Rey-Campos, J; Hillarp, A; Dahlbäck, B; Rodriguez de Cordoba, S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1990 EN
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36.6%
C4b-binding protein (C4BP) is an important component in the regulation of the complement system and also binds the anticoagulant vitamin K-dependent protein S. These activities are performed by distinct, although structurally related, polypeptides of 70 kDa (alpha chain) and 45 kDa (beta chain), respectively. In this report we have investigated the genetic relationships between these polypeptides. Using pulsed field gel electrophoresis analysis we demonstrate that the genes coding for the alpha (C4BP alpha) and beta (C4BP beta) chains are closely linked within the regulator of complement activation gene cluster. In addition, we have determined that the 3' end of the C4BP beta gene lies 3.5-5 kilobases from the 5' end of the C4BP alpha gene. These findings support the concept that the C4BP alpha and C4BP beta genes are the result of a gene duplication event.