RESUMO
We have analyzed a series of mutants derived from a KLH-specific, I-E-restricted T hybridoma (FN1-18) which have lost antigen-reactivity while retaining both T cell receptor idiotypic determinants and the ability to respond to Con A. The variants have not gained any detectable alloreactivity, nor is there an obvious lesion in the mutants' beta chain DNA containing the utilized beta chain genes. This loss of antigen reactivity is due to a failure of stable production of the specific V beta-containing mRNA. Our results indicate that in FN1-18, the T cell receptor antigenic determinants are most likely carried by the alpha chain alone or by a complementation product of the V alpha FN1-18 with the V beta of BW5147. V beta FN1-18 represents a previously undescribed T cell receptor V region.
Assuntos
Epitopos/imunologia , Genes/efeitos da radiação , Hibridomas/metabolismo , Mutação , Receptores de Antígenos de Linfócitos T/genética , Animais , Anticorpos Monoclonais/fisiologia , DNA/isolamento & purificação , Hemocianinas/imunologia , Antígenos de Histocompatibilidade Classe II/genética , Hibridomas/efeitos da radiação , Idiótipos de Imunoglobulinas/imunologia , Região Variável de Imunoglobulina/genética , Camundongos , Camundongos Endogâmicos AKR , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , RNA/isolamento & purificação , Receptores de Antígenos de Linfócitos T/efeitos da radiação , Linfócitos T/metabolismoRESUMO
Individual T cell receptor (TCR) Valpha elements are expressed preferentially in CD4 or CD8 peripheral T cell subsets. The closely related Valpha3.1 and Valpha3.2 elements show reciprocal selection into CD4 and CD8 subsets, respectively. Transgenic mice expressing site-directed mutants of a Valpha3.1 gene were used to show that individual residues in either the complementarity-determining region 1 (CDR1) or CDR2 were sufficient to change selection from the CD4 subset to the CD8 subset. Thus, the germline-encoded Valpha elements are a major influence on major histocompatibility class complex (MHC) restriction, most likely by a preferential interaction with one or the other class of MHC molecule.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Antígenos de Histocompatibilidade Classe II/imunologia , Antígenos de Histocompatibilidade Classe I/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/imunologia , Animais , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , Mutagênese Sítio-Dirigida , Receptores de Antígenos de Linfócitos T alfa-beta/química , Receptores de Antígenos de Linfócitos T alfa-beta/genética , TransgenesRESUMO
Recent results show that the repertoire of anti-MHC class 1-specific inhibitory receptors expressed by natural killer cells is influenced by self class 1 molecules in such a way as to minimize the number of cells with multiple self-reactive inhibitory receptors.
Assuntos
Antígenos Ly , Proteínas de Transporte/fisiologia , Células Matadoras Naturais/imunologia , Proteínas de Membrana/fisiologia , Animais , Proteínas de Transporte/genética , Regulação da Expressão Gênica , Antígenos H-2/fisiologia , Lectinas Tipo C , Proteínas de Membrana/genética , Receptores Semelhantes a Lectina de Células NK , Tolerância a Antígenos Próprios , Microglobulina beta-2/genética , Microglobulina beta-2/fisiologiaRESUMO
The thymic preference for CD4+ T cells over CD8+ T cells is often attributed to a default pathway favouring CD4+ T cells or to homeostatic mechanisms. It is also clear, however, that T-cell receptor (TCR) preferences for major histocompatibility complex (MHC) class I versus class II binding will strongly influence an individual clone's skewing to the CD4 or CD8 subset. The variable region of each TCR alpha chain (V alpha) studied to date is found to be overrepresented in either CD4+ or CD8+ cells, suggesting that each V alpha element can interact more favourably with either MHC class I or class II molecules. Indeed, TCRs appear to have an intrinsic ability to interact with MHC molecules, and single amino acid residues present in germline-encoded complementarity determining region 1 (CDR1) and CDR2 of the V alpha element can be responsible for determining MHC specificity. Interestingly, the degree of CD4/CD8 skewing is variable among different mouse strains and in human populations. Here, we have shown that polymorphism in CD4/CD8 skewing between B6 and BALB/c mice is determined by the stem cell genotype and not by environmental effects, and that it maps in or near the TCR alpha-chain complex, Tcra. This was confirmed by comparing Tcra(b) with Tcra(a) or Tcra(c) haplotypes in congenic mice. We propose that the array of V alpha genes in various Tcra haplotypes exerts influence over the proportion of CD4 and CD8 subsets generated and may account in part for the observed thymic skewing. Thus, while it has been suggested that the TCR genes have been selected by evolution for MHC binding, our results further indicate selection for class II MHC preference.
Assuntos
Mapeamento Cromossômico , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Timo/citologia , Animais , Antígenos CD4 , Relação CD4-CD8 , Antígenos CD8 , Genótipo , Células-Tronco Hematopoéticas/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Polimorfismo GenéticoRESUMO
Superantigens stimulate powerful T-cell responses that can have marked effects in vivo, sometimes leading to shock or even death. The demonstration that strong T-cell responses to superantigens in vivo can be followed by tolerance, reflecting either clonal elimination or anergy, has provided important insights into how mature T cells can be regulated. Further progress in understanding the factors that control these responses relies heavily on defining the specific interactions between T-cell receptors, superantigens and major histocompatibility complex molecules which lead to T-cell activation as well as on the characterization of the specific signal transduction events and molecules involved in this activation. Significant progress has been made, during the past year, in the first area and these findings are summarized below; though less information is available in the latter area, recent observations relevant to this issue are discussed.
Assuntos
Ativação Linfocitária , Superantígenos/imunologia , Linfócitos T/imunologia , Animais , Antígenos de Histocompatibilidade Classe II/imunologia , Humanos , Tolerância Imunológica , Receptores de Antígenos de Linfócitos T/imunologia , Superantígenos/químicaRESUMO
Macrophages play a central role in infections, as a target for pathogens and in activation of the immune system. Interleukin-10 (IL-10), a cytokine produced by macrophages, is a potent immunosuppressive factor. Some intracellular pathogens specifically target macrophages for infection and use IL-10 to dampen the host immune response and stall their elimination from the host. Certain viruses induce production of cellular IL-10 by macrophages, whereas other viruses encode their own viral IL-10 homologs. Additionally, specific bacteria, including several Mycobacteria spp. and Listeria monocytogenes, can survive and replicate in macrophages while inducing cellular IL-10, highlighting a potential role for IL-10 of macrophage origin in the immunosuppressive etiology of these pathogens. Thus, the exploitation of IL-10 appears to be a common mechanism of immunosuppression by a diverse group of intracellular pathogens that can infect macrophages.
Assuntos
Citomegalovirus/imunologia , HIV-1/imunologia , Tolerância Imunológica , Interleucina-10/biossíntese , Macrófagos/microbiologia , Macrófagos/virologia , Mycobacterium tuberculosis/imunologia , Infecções por Citomegalovirus/imunologia , Infecções por Citomegalovirus/virologia , Infecções por HIV/imunologia , Humanos , Interleucina-10/imunologia , Macrófagos/imunologia , Tuberculose/imunologia , Tuberculose/microbiologiaRESUMO
Superantigens interact with the immune system by binding to major histocompatibility complex (MHC) class II proteins and activating T cells through the variable region of the T cell receptor beta-chain. Through this means they can cause massive proliferation and then death of a large proportion of T cells. Superantigens are produced by bacteria, mycoplasmas, retroviruses, and probably by other organisms. In some cases, the superantigen is crucial to the organism's life cycle. Mouse mammary tumor virus disseminates by activating T cells which stimulate the proliferation of B cells harboring the virus. In other cases, the superantigen may be responsible for the pathogenesis of the infection, such as in the case of Toxic Shock Syndrome. In this article, we review information on the diseases in which superantigens are involved, and the mechanisms by which the superantigens interact with T cell receptor and class II molecules.
Assuntos
Sistema Imunitário/fisiologia , Superantígenos/fisiologia , Animais , Antígenos de Histocompatibilidade Classe II/metabolismo , Antígenos de Histocompatibilidade Classe II/fisiologia , Humanos , Sistema Imunitário/metabolismo , Ligação Proteica , Receptores de Antígenos de Linfócitos T/metabolismo , Receptores de Antígenos de Linfócitos T/fisiologia , Superantígenos/metabolismo , Linfócitos T/imunologia , Linfócitos T/metabolismo , Linfócitos T/fisiologiaRESUMO
The kinetics of the interaction between T cell receptor (TCR) and major histocompatibility complex (MHC) has an important role in determining thymocyte-positive and -negative selection in the thymus, as well as in T cell activation. The alpha chain of the TCR is the major player in determining how the TCR fits onto the MHC ligand, and thus has a major role in determining whether a T cell develops as class I or class II restricted. In this article, we summarize recent data from our laboratory and others on the role of polymorphism in the Valpha combining site in determining MHC class restriction, and on kinetic parameters in thymocyte selection.
Assuntos
Complexo Principal de Histocompatibilidade/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/imunologia , Linfócitos T/imunologia , Animais , Humanos , Cinética , Ativação Linfocitária , Complexo Principal de Histocompatibilidade/genética , Polimorfismo Genético , Receptores de Antígenos de Linfócitos T alfa-beta/genéticaRESUMO
We have expressed the superantigen staphylococcal enterotoxin A (SEA) on the surface of bacteriophage as a fusion with the gene VIII protein (gVIIIp). This phage-displayed superantigen retains the properties inherent in the natural protein. It binds to MHC class II and activates T-cells bearing appropriate V beta regions. A flexible 5-amino acid linker sequence between the SEA molecule and the phage coat protein improved the production of functional phage-displayed SEA. Binding to MHC class II-expressing cells effectively selected SEA-phage from non-SEA-phage background. This indicates that this will be an effective method for selecting new specificities of superantigen from libraries of SEA mutants and for cloning of novel superantigens.
Assuntos
Bacteriófagos , Enterotoxinas/imunologia , Vetores Genéticos , Antígenos de Histocompatibilidade Classe II/imunologia , Superantígenos/imunologia , Sequência de Aminoácidos , Animais , Sequência de Bases , DNA Bacteriano , Enterotoxinas/genética , Dados de Sequência Molecular , Coelhos , Receptores de Antígenos de Linfócitos T alfa-beta/imunologia , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Superantígenos/genética , Células Tumorais CultivadasRESUMO
An approach has been devised for analysing data generated in the study of in vivo cytotoxic T cell responses. The method calculates the total number of lytic units generated in the peritoneal cavity, or in cultures of the lymph nodes draining the rear footpad, following antigenic stimulation. The assessment of group differences is facilitated, and the method lends itself to computerised and hence objective data analysis.
Assuntos
Citotoxicidade Imunológica , Linfócitos T/imunologia , Animais , Células Cultivadas , Computadores , Cinética , Linfonodos/imunologia , Complexo Principal de Histocompatibilidade , Camundongos , Camundongos Endogâmicos CBA , Camundongos Endogâmicos , Especificidade da EspécieAssuntos
Células Apresentadoras de Antígenos/imunologia , Antígenos de Superfície/imunologia , Isoantígenos/imunologia , Linfócitos T/imunologia , Animais , Linfócitos B/imunologia , Ativação Linfocitária , Camundongos , Linfócitos T Citotóxicos/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Linfócitos T Reguladores/imunologiaRESUMO
The T cell receptor (TCR) beta-chain is produced in the endoplasmic reticulum where it associates with the TCR alpha-chain and the members of the CD3 complex to form the complete receptor. When the other chains of the complex are not available, the beta-chain is rapidly degraded within the endoplasmic reticulum. When incomplete TCR.CD3 complexes are formed, they are transported through the Golgi apparatus and degraded in lysosomes. In this study, a truncated form of the TCR beta-chain has been made by removal of the transmembrane and cytoplasmic segments. Unlike the normal beta-chain, the truncated molecule is stable and is transported through the Golgi apparatus and secreted. This process occurs at a similar rate in both T and B cells, indicating that it is not affected by the presence or absence of CD3 components. These data suggest that an element in the transmembrane or cytoplasmic region of the beta-chain confers sensitivity to the degradative control mechanisms that regulate TCR expression.
Assuntos
Antígenos CD/metabolismo , Antígenos de Diferenciação de Linfócitos T/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismo , Acetilglucosaminidase/farmacologia , Sequência de Aminoácidos , Animais , Linfócitos B/metabolismo , Linfócitos B/ultraestrutura , Sequência de Bases , Transporte Biológico , Complexo CD3 , Clonagem Molecular , Retículo Endoplasmático , Expressão Gênica , Glicosilação , Complexo de Golgi/metabolismo , Técnicas de Imunoadsorção , Substâncias Macromoleculares , Manosil-Glicoproteína Endo-beta-N-Acetilglucosaminidase , Camundongos , Dados de Sequência Molecular , Mutação , Conformação Proteica , Processamento de Proteína Pós-Traducional , Receptores de Antígenos de Linfócitos T/genética , Homologia de Sequência do Ácido Nucleico , Linfócitos T/metabolismo , Linfócitos T/ultraestrutura , Transfecção , Células Tumorais CultivadasRESUMO
While it has been widely reported that some subsets of suppressor T cells are restricted by products of immunoglobulin heavy chain genes (particularly the variable region gene), we have been unable to find evidence for such interactions in the suppression of the primary in vivo cytotoxic T cell response to minor alloantigen. We have also examined the repertoire of the suppressor T cells active in this system and find that they recognize a different set of antigens from cytotoxic T cells, out of the same available pool of minor antigens.
Assuntos
Genes , Cadeias Pesadas de Imunoglobulinas/genética , Isoantígenos/genética , Linfócitos T Reguladores/imunologia , Linfócitos T/imunologia , Animais , Reações Cruzadas , Tolerância Imunológica , Região Variável de Imunoglobulina/genética , Camundongos , Camundongos Endogâmicos , Especificidade da EspécieRESUMO
Bacterial toxin superantigens bind to MHC class II molecules and activate a large proportion of T cells through a direct interaction with the T cell receptor (TCR). The toxin: TCR interaction involves specific recognition between the beta-chain variable region and the toxin. Although a complete alpha beta T cell receptor is required for activation of T cells, studies using purified soluble T cell receptor beta-chain have shown that it alone is sufficient for binding the toxin: class II complex. The regions of V beta and enterotoxin involved in the recognition have been determined.
Assuntos
Antígenos de Bactérias/metabolismo , Receptores de Antígenos de Linfócitos T alfa-beta/metabolismo , Animais , Antígenos Virais/metabolismo , Sítios de Ligação , Enterotoxinas/imunologia , Antígenos de Histocompatibilidade Classe II/metabolismo , Humanos , Ativação Linfocitária , Retroviridae/imunologia , Linfócitos T/imunologiaRESUMO
The interaction of the T-cell receptor (TCR) with peptide antigen plus major histocompatibility complex (MHC) protein requires both alpha and beta chains of the TCR. The "superantigens" are a group of molecules that are recognized in association with MHC class II but that do not appear to conform to this pattern. Superantigens are defined as such because they cause the activation or thymic deletion of many or all T cells bearing specific TCR beta-chain variable region (V beta) elements. The strong association of particular V beta S with T-cell responses to superantigens suggests that their interaction with the TCR is fundamentally different from that of most antigens. We have directly investigated the involvement of the beta chain in recognition of a superantigen by using a secreted, truncated TCR beta chain and the bacterial superantigen staphylococcal enterotoxin A complexed to cell-surface MHC class II. We demonstrate that this interaction is specific for the enterotoxin and is dependent on MHC class II expression by the cell. The reaction can be inhibited by antibodies against the three components of the reaction: V beta, enterotoxin, and class II. This shows that the TCR beta chain is sufficient to mediate the interaction with a superantigen-class II complex. The TCR alpha chain and co-receptors such as CD4 are not required.