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2.
Eur J Immunol ; 31(7): 2189-99, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11449373

RESUMO

The more severe phenotype of mice lacking CD19 as compared to CD21 suggests that a complement-independent ligand for the CD19/CD21 complex exists. We sought ligands for CD19 by examining binding reactions with fusion proteins comprised of the extracellular region of CD19 and the Fc region of IgG1. A fusion protein containing the third extracellular domain (D3-Fc) bound to WEHI-231 cells, and this was competed by soluble IgM. This function of IgM was confirmed by the binding of D3-Fc to beads coated with IgM. A second ligand for D3-Fc was found on stromal cells, and was shown to be heparin/heparan sulfate. These two ligands would be considered to reside on follicular dendritic cells, and may account for the observed ability of D3-Fc to bind to sites in germinal centers containing these cells.


Assuntos
Antígenos CD19/imunologia , Antígenos CD19/metabolismo , Heparina/metabolismo , Heparitina Sulfato/metabolismo , Imunoglobulina M/imunologia , Células Estromais/imunologia , Animais , Antígenos CD19/genética , Linhagem Celular , Células Cultivadas , Proteínas do Sistema Complemento/imunologia , Células Dendríticas/imunologia , Centro Germinativo/imunologia , Imunoglobulina G/genética , Ligantes , Camundongos , Camundongos Endogâmicos BALB C , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão/metabolismo , Células Estromais/química
3.
Science ; 293(5528): 248-50, 2001 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-11452114

RESUMO

Vaccination for persistent viral or bacterial infections must program the immune system for a lifelong need to generate antigen-specific effector lymphocytes. How the immune system does this is not known, but recent studies have shown that a subset of B lymphocytes, the germinal center B cell, is capable of self-renewal because it expresses a transcriptional repressor, BCL6, that blocks terminal differentiation. If a similar mechanism for arresting differentiation exists for long-lived, antigen-selected lymphocytes, a stem cell-like capacity for self-renewal could be the basis for the continual generation of effector lymphocytes from the memory pool. Understanding how to regulate the terminal differentiation of lymphocytes will improve immunotherapeutic approaches for chronic infectious diseases and cancer.


Assuntos
Diferenciação Celular , Memória Imunológica , Linfócitos/imunologia , Vacinação , Animais , Linfócitos B/imunologia , Proteínas de Ligação a DNA/fisiologia , Humanos , Leucopoese , Linfócitos/citologia , Proteínas Proto-Oncogênicas/fisiologia , Proteínas Proto-Oncogênicas c-bcl-6 , Receptores de Antígenos/imunologia , Células-Tronco , Linfócitos T/imunologia , Fatores de Transcrição/fisiologia
4.
J Exp Med ; 192(12): 1841-8, 2000 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-11120780

RESUMO

Lymphocytes usually differentiate into effector cells within days after antigen exposure, except in germinal centers where terminal differentiation is delayed while somatic hypermutation creates high-affinity antibody mutants. Here we investigate whether arrest of terminal differentiation can be mediated by BCL-6, a transcriptional repressor that is expressed by germinal center B cells and is required for this phase of B cell development. We find that BCL-6 suppresses the differentiation of transformed and primary B cells to plasma cells by inhibiting the signal transducer and activator of transcription 3-dependent expression of the major regulator of plasma cell development, the B lymphocyte-induced maturation protein (Blimp-1). This function of BCL-6 as a repressor of B lymphocyte differentiation may also underlie the association between chromosomal translocations of its gene and B cell lymphomas.


Assuntos
Linfócitos B/citologia , Diferenciação Celular , Proteínas de Ligação a DNA/antagonistas & inibidores , Proteínas de Ligação a DNA/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Transativadores/antagonistas & inibidores , Fatores de Transcrição/metabolismo , Animais , Linfócitos B/efeitos dos fármacos , Linfócitos B/metabolismo , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Citocinas/farmacologia , Proteínas de Ligação a DNA/genética , Citometria de Fluxo , Camundongos , Plasmócitos/citologia , Plasmócitos/efeitos dos fármacos , Plasmócitos/metabolismo , Fator 1 de Ligação ao Domínio I Regulador Positivo , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-bcl-6 , Proteínas Repressoras/metabolismo , Fator de Transcrição STAT3 , Transativadores/metabolismo , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/genética
5.
Eur J Immunol ; 30(10): 2881-7, 2000 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11069070

RESUMO

Innate immunity directs the adaptive immune response by identifying antigens that are associated with infectious agents. Although some microbial antigens can be recognized by innate immune receptors, most cannot, and these require identification by some other means. The introduction of aldehydes into antigens by glycolaldehyde, which can be produced by activated neutrophils reacting with serine, or by the oxidation of an N-linked oligosaccharide with NaIO4, enhances by several orders of magnitude their immunogenicity in mice. The augmented immunogenicity requires the presence of an aldehyde on the antigen, and is not dependent on protein aggregation. An in vitro correlate of augmented immunogenicity is the enhanced presentation of glycolaldehyde-modified antigen to T cells by macrophages and bone marrow-derived dendritic cells. The potential clinical importance of this form of antigen modification is twofold: glycolaldehyde renders a model self antigen immunogenic, and it converts a relatively non-immunogenic malaria antigen, merozoite surface protein-1, into an effective immunogen. Thus, the tagging of antigens by the addition of aldehydes, which may be an innate immune mechanism to facilitate their recognition by the adaptive immune system, may have a role in the genesis of autoimmunity and the development of vaccines.


Assuntos
Acetaldeído/análogos & derivados , Aldeídos/imunologia , Formação de Anticorpos/imunologia , Antígenos/imunologia , Imunidade Inata/imunologia , Acetaldeído/imunologia , Animais , Antígenos/química , Antígenos de Protozoários/química , Antígenos de Protozoários/imunologia , Autoantígenos/química , Autoantígenos/imunologia , Autoimunidade/imunologia , Galinhas , Columbidae , Grupo dos Citocromos c/química , Grupo dos Citocromos c/imunologia , Proteína 1 de Superfície de Merozoito/química , Proteína 1 de Superfície de Merozoito/imunologia , Camundongos , Muramidase/química , Muramidase/imunologia , Neutrófilos/imunologia , Ovalbumina/química , Ovalbumina/imunologia , Oxirredução , Ácido Periódico/farmacologia , Serina/metabolismo , Relação Estrutura-Atividade , Vacinas
6.
Annu Rev Immunol ; 18: 393-422, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10837064

RESUMO

The membrane protein complex CD19/CD21 couples the innate immune recognition of microbial antigens by the complement system to the activation of B cells. CD21 binds the C3d fragment of activated C3 that becomes covalently attached to targets of complement activation, and CD19 co-stimulates signaling through the antigen receptor, membrane immunoglobulin. CD21 is also expressed by follicular dendritic cells and mediates the long-term retention of antigen that is required for the maintenance of memory B cells. Understanding of the biology of this receptor complex has been enriched by analyses of genetically modified mice; these analyses have uncovered roles not only in positive responses to foreign antigens, but also in the development of tolerance to self-antigens. Studies of signal transduction have begun to determine the basis for the coreceptor activities of CD19. The integration of innate and adaptive immune recognition at this molecular site on the B cell guides the appropriate selection of antigen by adaptive immunity and emphasizes the importance of this coreceptor complex.


Assuntos
Antígenos CD19/imunologia , Linfócitos B/imunologia , Moléculas de Adesão Celular , Lectinas , Receptores de Complemento 3d/imunologia , Transdução de Sinais/imunologia , Animais , Antígenos CD/imunologia , Antígenos de Diferenciação de Linfócitos B/imunologia , Humanos , Camundongos , Receptores de IgG/imunologia , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico
11.
Semin Immunol ; 10(5): 355-61, 1998 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-9799710

RESUMO

The complement system covalently attaches C3d to microbial antigens which binds to CR2 on B lymphocytes, leading to a markedly enhanced adaptive immune response to that antigen. The enhancement is mediated by the cross-linking of the CR2-CD19 complex to mIg which augments the activation of several intracellular signalling pathways. Two additional receptors of the B lymphocyte, FcgammaRIIB and CD22, have opposing effects when cross-linked to mIg, the former suppressing signalling by recruiting the inositol phosphatase, SHIP, and the latter by activating the phosphotyrosine phosphatase, SHP-1. Two principles emerge from these studies: innate immunity guides the adaptive immune response, and activation of the B lymphocyte is determined by co-receptors which evaluate the biological characteristics of antigen.


Assuntos
Moléculas de Adesão Celular , Proteínas do Sistema Complemento/fisiologia , Imunidade , Lectinas , Animais , Antígenos CD/fisiologia , Antígenos CD19/fisiologia , Antígenos de Diferenciação de Linfócitos B/fisiologia , Linfócitos B/imunologia , Complemento C3/fisiologia , Humanos , Ativação Linfocitária , Receptores de Complemento 3d/fisiologia , Receptores de IgG/fisiologia , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico
12.
J Immunol ; 161(6): 3176-85, 1998 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-9743386

RESUMO

Despite the recent success of mAb in the treatment of certain malignancies, there is still considerable uncertainty about the mechanism of action of anti-cancer Abs. Here, a panel of rat anti-mouse B cell mAb, including Ab directed at surface IgM Id, CD19, CD22, CD40, CD74, and MHC class II, has been investigated in the treatment of two syngeneic mouse B cell lymphomas, BCL1 and A31. Only three mAb were therapeutically active in vivo, anti-Id, anti-CD19, and anti-CD40. mAb to the other Ags showed little or no therapeutic activity in either model despite giving good levels of surface binding and activity in Ag-dependent cellular cytotoxicity and complement assays, and in some cases inhibiting cell growth in vitro. We conclude that the activity of mAb in vitro does not predict therapeutic performance in vivo. Furthermore, in vivo tracking experiments using fluorescently tagged cells showed that anti-Id and anti-CD40 mAb probably operate via different mechanisms: the anti-Id mAb cause growth arrest that is almost immediate and does not eliminate cells over a period of 5 or 6 days, and the anti-CD40 mAb have a delayed effect that allows tumor to grow normally for 3 days, but then abruptly eradicates lymphoma cells. This work supports the belief that mAb specificity is critical to therapeutic success in lymphoma and that, in addition to any effector-recruiting activity they may possess, in vivo mAb operate via mechanisms that involve cross-linking and signaling of key cellular receptors.


Assuntos
Linfoma de Células B/imunologia , Transdução de Sinais/imunologia , Animais , Anticorpos Monoclonais/metabolismo , Anticorpos Monoclonais/farmacocinética , Anticorpos Monoclonais/farmacologia , Anticorpos Monoclonais/uso terapêutico , Citotoxicidade Celular Dependente de Anticorpos , Sítios de Ligação de Anticorpos , Divisão Celular/imunologia , Proteínas do Sistema Complemento/fisiologia , Testes Imunológicos de Citotoxicidade , Modelos Animais de Doenças , Fluoresceínas/farmacocinética , Corantes Fluorescentes/farmacocinética , Imunização Passiva , Linfoma de Células B/metabolismo , Linfoma de Células B/patologia , Linfoma de Células B/terapia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos CBA , Succinimidas/farmacocinética , Células Tumorais Cultivadas
13.
Immunity ; 8(5): 635-45, 1998 May.
Artigo em Inglês | MEDLINE | ID: mdl-9620684

RESUMO

CD19 is a coreceptor that amplifies signaling by membrane immunoglobulin (mIg) to promote responses of the B lymphocyte to T-dependent antigens. Vav is a guanine nucleotide exchange factor for the Rho, Rac, Cdc42 family of small GTPases. We found that coligating mIg and CD19 causes a synergistic increase in the tyrosine phosphorylation of CD19. Phosphorylated tyrosine-391 of CD19 binds Vav to mediate a sustained increase in intracellular Ca2+ concentration. This response correlates with activation by the CD19-Vav complex of phosphatidylinositol 4-phosphate 5-kinase for the synthesis of phosphatidylinositol 4,5-bisphosphate. Interaction of CD19 with Vav also mediates the synergistic activation of the mitogen-activated protein kinase JNK. Therefore, CD19 is a membrane adaptor protein that recruits Vav for the activation of lipid and protein kinases.


Assuntos
Antígenos CD19/metabolismo , Linfócitos B/enzimologia , Proteínas de Ciclo Celular , Proteínas Quinases JNK Ativadas por Mitógeno , Quinases de Proteína Quinase Ativadas por Mitógeno , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Proteínas Quinases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Animais , Cálcio/metabolismo , Células Cultivadas , Ativação Enzimática , Fatores de Troca do Nucleotídeo Guanina , Humanos , MAP Quinase Quinase 4 , Camundongos , Fosforilação , Ligação Proteica , Proteínas/metabolismo , Proteínas Proto-Oncogênicas c-vav , Ratos , Tirosina/metabolismo
14.
J Exp Med ; 187(5): 807-11, 1998 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-9480991

RESUMO

Mice in which the Lyn, Cd22, or Shp-1 gene has been disrupted have hyperactive B cells and autoantibodies. We find that in the absence of Lyn, the ability of CD22 to become tyrosine phosphorylated after ligation of mIg, to recruit SHP-1, and to suppress mIg-induced elevation of intracellular [Ca2+] is lost. Therefore, Lyn is required for the SHP-1-mediated B cell suppressive function of CD22, accounting for similarities in the phenotypes of these mice.


Assuntos
Antígenos CD/fisiologia , Antígenos de Diferenciação de Linfócitos B/fisiologia , Autoimunidade , Linfócitos B/fisiologia , Moléculas de Adesão Celular , Lectinas , Proteínas Tirosina Fosfatases/fisiologia , Receptores de Antígenos de Linfócitos B/fisiologia , Quinases da Família src/fisiologia , Sequência de Aminoácidos , Animais , Cálcio/fisiologia , Tolerância Imunológica , Peptídeos e Proteínas de Sinalização Intracelular , Camundongos , Camundongos Knockout , Fosforilação , Fosfotirosina/metabolismo , Proteína Tirosina Fosfatase não Receptora Tipo 11 , Proteína Tirosina Fosfatase não Receptora Tipo 6 , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico , Transdução de Sinais , Baço/citologia
16.
J Exp Med ; 186(9): 1575-83, 1997 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-9348315

RESUMO

We wish to identify developmental changes in germinal center B cells that may contribute to their rapid growth. SHP-1 is an SH2 domain-containing phosphotyrosine phosphatase that negatively regulates activation of B cells and other cells of hematopoietic lineages. We have found that in all 13 EBV-negative and 11 EBV-positive Burkitt lymphomas with a nonlymphoblastoid phenotype, the mean concentration of SHP-1 was reduced to 5% of that of normal B and T cells. The possibility that this diminished expression of SHP-1 was related to the germinal center phenotype of Burkitt lymphomas was supported by the low to absent immunofluorescent staining for SHP-1 in germinal centers, and by the inverse relationship between the concentration of SHP-1 and the expression of the germinal center marker CD38 on purified tonsillar B cells. In CD38-high B cells, SHP-1 concentration was 20% of that of mantle zone B cells from the same donor. This reduction in SHP-1 is comparable to that of cells from motheaten viable mev/mev mice in which there is dysregulated, spontaneous signaling by cytokine and antigen receptors. Therefore, germinal center B cells may have a developmentally regulated, low threshold for cellular activation.


Assuntos
Linfócitos B/enzimologia , Linfoma de Burkitt/enzimologia , Regulação para Baixo , Centro Germinativo/enzimologia , Proteínas Tirosina Fosfatases/biossíntese , Linfócitos B/citologia , Linfoma de Burkitt/genética , Linfoma de Burkitt/imunologia , Diferenciação Celular/imunologia , Regulação da Expressão Gênica/efeitos dos fármacos , Centro Germinativo/citologia , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Plasmídeos , Proteína Tirosina Fosfatase não Receptora Tipo 11 , Proteína Tirosina Fosfatase não Receptora Tipo 6 , Proteínas Tirosina Fosfatases/genética , Proteínas Tirosina Fosfatases Contendo o Domínio SH2 , Tetraciclina/farmacologia , Transfecção , Células Tumorais Cultivadas
18.
Immunity ; 7(1): 59-67, 1997 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9252120

RESUMO

The signaling pathways linked to membrane immunoglobulin (mIg) that are regulated by the coreceptors CD19 and CD22 are not known. The mitogen-activated protein (MAP) kinases ERK2, JNK, and p38 couple extracellular signals to transcriptional responses. The capacity of mIg to activate these MAP kinases is synergistically amplified by coligating CD19, and this effect requires that CD19 be juxtaposed to mIg. CD22 suppresses MAP kinase activation when cross-linked to mIg alone or to the coligated complex of mIg and CD19. Separate ligation and sequestration of CD22 from mIg enhances MAP kinase activation, probably reflecting release of mIg from constitutive down-regulation. Thus, CD19 and CD22 have counterregulatory effects on MAP kinase activation by mIg, which are dependent on their proximity to the antigen receptor.


Assuntos
Antígenos CD19/metabolismo , Antígenos CD/metabolismo , Antígenos de Diferenciação de Linfócitos B/metabolismo , Linfócitos B/enzimologia , Proteínas Quinases Dependentes de Cálcio-Calmodulina/metabolismo , Moléculas de Adesão Celular/metabolismo , Lectinas , Proteínas Quinases Ativadas por Mitógeno , Receptores de Antígenos de Linfócitos B/metabolismo , Animais , Linfócitos B/imunologia , Ativação Enzimática , Proteínas Quinases JNK Ativadas por Mitógeno , Camundongos , Camundongos Endogâmicos BALB C , Proteína Quinase 1 Ativada por Mitógeno , Ligação Proteica , Proteínas Tirosina Quinases/metabolismo , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico , Proteínas Quinases p38 Ativadas por Mitógeno
19.
Curr Opin Immunol ; 9(3): 324-9, 1997 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9203413

RESUMO

The past year has seen advances in our understanding of accessory membrane proteins that modulate the B cell response to antigen-receptor stimulation. The generation of complement receptor deficient mice has reinforced our appreciation of the importance of complement receptors in the B cell response to antigen. The association of inositol polyphosphate 5-phosphatase with FcgammaRIIB suggests another mechanism, in addition to recruitment of the phosphotyrosine phosphatase SHP-1, by which secreted immunoglobulin can limit further response to antigen. The in vivo function of CD22 in regulating the threshold of antigen-receptor signalling has been shown using CD22-deficient mice. Lastly, B cell receptor signalling in the B-1 subset of B lymphocytes has been demonstrated to be negatively regulated by CD5.


Assuntos
Linfócitos B/imunologia , Moléculas de Adesão Celular , Lectinas , Receptores Imunológicos/imunologia , Transdução de Sinais/imunologia , Animais , Antígenos CD/imunologia , Antígenos CD19/imunologia , Antígenos de Diferenciação de Linfócitos B/imunologia , Humanos , Ativação Linfocitária/imunologia , Camundongos , Receptores Fc/imunologia , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico
20.
J Immunol ; 158(7): 3062-9, 1997 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-9120258

RESUMO

CD19 enhances membrane IgM (mIgM) signaling and is required for B lymphocyte responses to T-dependent Ags. CD19 is tyrosine phosphorylated when mIgM is ligated and binds SH2 domain-containing signaling proteins. We suggest that the basis for phosphorylation is the association of CD19 with Syk and other components of the mIgM complex. IgM, CD22, Ig-alpha, Ig-beta, and Syk were coimmunoprecipitated with CD19 from detergent lysates of B lymphocytes. The association was maintained with a chimeric form of CD19 containing only the transmembrane domain and the membrane proximal 17 amino acids of the cytoplasmic domain encoded by exon 6. This sequence is sufficient to mediate the association, as a synthetic peptide of the exon 6-encoded region adsorbs IgM and Syk. Deletion of the juxtamembrane 17 amino acids of the cytoplasmic domain encoded by CD19 exon 6 abolishes association of CD19 with the mIgM complex. Deletion of these amino acids, which contain no tyrosines, also reduces mIgM-induced tyrosine phosphorylation of the remainder of the CD19 cytoplasmic domain. Coligating this mutant CD19 to mIgM restores phosphorylation. Thus, a discrete region of the cytoplasmic domain regulates the tyrosine phosphorylation of CD19 in the activation of B cells by mIgM.


Assuntos
Antígenos CD19/fisiologia , Imunoglobulina M/farmacologia , Receptores de Antígenos de Linfócitos B/metabolismo , Receptores de Antígenos de Linfócitos B/farmacologia , Tirosina/metabolismo , Sequência de Aminoácidos , Antígenos CD19/genética , Autorradiografia , Humanos , Dados de Sequência Molecular , Fosforilação , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão/química , Transdução de Sinais/imunologia , Células Tumorais Cultivadas
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