RESUMO
To determine the cellular targets for glucocorticoid (GC) action, we have generated mice in which a green fluorescent protein-glucocorticoid receptor (GFP-GR) fusion gene is knocked into the endogenous GR locus. We found that GFP-GR function is indistinguishable from endogenous GR on both a cellular and systemic level. Furthermore, the green fluorescence intensity of the GFP-GR protein is proportional to its expression, allowing quantitation of GR expression in single living cells. We initiated our analysis of GR regulation in the thymus. Using multicolor flow cytometry, we found that GR expression is uniform among embryonic thymocyte subpopulations, but gradually "matures" over a three-week period after birth. In the adult, analysis of GFP-GR expression on RAG2-/- and HY T cell receptor (TCR) transgenic genetic backgrounds, showed that GR is induced to high levels in immature CD25+ CD4- CD8- thymocytes and down-regulated by activation of the pre-TCR during positive but not negative selection. Additionally, relative GR expression is dissociated from GC-induced apoptosis in vivo. These results implicate pre-TCR signaling as a mechanism for GR down-regulation and separate receptor abundance from susceptibility to apoptosis across thymocyte populations.
Assuntos
Receptores de Glucocorticoides/metabolismo , Animais , Apoptose , Dexametasona/farmacologia , Proteínas de Fluorescência Verde , Proteínas Luminescentes/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Receptores de Glucocorticoides/genética , Proteínas Recombinantes de Fusão , Timo/efeitos dos fármacos , Timo/fisiologiaRESUMO
Using a TCRalpha chain knock-in mouse, we demonstrate that V-gene replacement can operate in the T cell receptor alpha locus. Functional TCRalpha chain transcripts generated by Valpha-gene replacement at the site of the Valpha-embedded heptamer were identified in splenic T cells. This finding shows that Valpha-gene replacement can likely be used to shape the peripheral T cell repertoire. The conservation of the embedded heptamer in most Valpha segments adds support to the notion that V-gene replacement is a mechanism maintained to diversify the immune system and that argues that it is common to B and T cells.
Assuntos
Genes Codificadores da Cadeia alfa de Receptores de Linfócitos T , Região Variável de Imunoglobulina/genética , Animais , Complexo CD3/análise , Antígenos CD4/análise , Rearranjo Gênico , Genes Codificadores da Cadeia beta de Receptores de Linfócitos T , Camundongos , Camundongos Knockout , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Linfócitos T/metabolismoRESUMO
We generated transgenic mice that expressed hen egg-white lysozyme (HEL) under a class II MHC promoter. The A7 line expressed HEL with a point mutation in the Asp(52) residue, the main anchor amino acid responsible for the selection of the chemically dominant family of peptides (52-60) by I-A(k) molecules. Mice expressing HEL with Ala(52) were completely unresponsive when immunized with the same protein, i.e., HEL A52. However, the same mice immunized with wild-type HEL elicited T cells that recognized a conformation of the 52-61 core sequence uniquely different between Asp(52) and Ala(52) containing peptides. Importantly, some T cells also recognized the HEL A52 peptide given exogenously but not the same peptide processed from HEL A52 protein. Thus, a core MHC anchor residue influences markedly the specificity of the T cells. We discuss the relevance of these findings to autoimmunity and vaccination with altered peptides.
Assuntos
Ácido Aspártico/genética , Antígenos de Histocompatibilidade Classe II/metabolismo , Ativação Linfocitária , Muramidase/imunologia , Muramidase/metabolismo , Fragmentos de Peptídeos/metabolismo , Subpopulações de Linfócitos T/imunologia , Alanina/genética , Sequência de Aminoácidos , Animais , Apresentação de Antígeno/genética , Ácido Aspártico/imunologia , Diferenciação Celular/genética , Diferenciação Celular/imunologia , Sobrevivência Celular/genética , Sobrevivência Celular/imunologia , Antígenos de Histocompatibilidade Classe II/imunologia , Tolerância Imunológica/genética , Ativação Linfocitária/genética , Substâncias Macromoleculares , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Dados de Sequência Molecular , Muramidase/genética , Fragmentos de Peptídeos/imunologia , Mutação Puntual , Conformação Proteica , Subpopulações de Linfócitos T/citologiaRESUMO
Although interleukin (IL)-12 and IL-4 polarize naive CD4(+) T cells toward T helper cell type 1 (Th1) or Th2 phenotypes, it is not known whether cytokines instruct the developmental fate in uncommitted progenitors or select for outgrowth of cells that have stochastically committed to a particular fate. To distinguish these instructive and selective models, we used surface affinity matrix technology to isolate committed progenitors based on cytokine secretion phenotype and developed retroviral-based tagging approaches to directly monitor individual progenitor fate decisions at the clonal and population levels. We observe IL-4-dependent redirection of phenotype in cells that have already committed to a non-IL-4-producing fate, inconsistent with predictions of the selective model. Further, retroviral tagging of naive progenitors with the Th2-specific transcription factor GATA-3 provided direct evidence for instructive differentiation, and no evidence for the selective outgrowth of cells committed to either the Th1 or Th2 fate. These data would seem to exclude selection as an exclusive mechanism in Th1/Th2 differentiation, and support an instructive model of cytokine-driven transcriptional programming of cell fate decisions.
Assuntos
Diferenciação Celular/imunologia , Proteínas de Ligação a DNA/metabolismo , Células Th2/imunologia , Células Th2/metabolismo , Transativadores/metabolismo , Animais , Diferenciação Celular/efeitos dos fármacos , Divisão Celular , Linhagem Celular , Separação Celular/métodos , Células Clonais/citologia , Células Clonais/imunologia , Células Clonais/metabolismo , Citocinas/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/farmacologia , Fator de Transcrição GATA3 , Imunofenotipagem , Interferon gama/biossíntese , Interferon gama/metabolismo , Interleucina-4/biossíntese , Interleucina-4/metabolismo , Camundongos , Retroviridae/genética , Fator de Transcrição STAT6 , Células-Tronco/citologia , Células-Tronco/imunologia , Células-Tronco/metabolismo , Processos Estocásticos , Células Th1/citologia , Células Th1/imunologia , Células Th1/metabolismo , Células Th2/citologia , Transativadores/deficiência , Transativadores/genética , Transativadores/farmacologia , TransfecçãoRESUMO
GADS is an adaptor protein implicated in CD3 signaling because of its ability to link SLP-76 to LAT. A GADS-deficient mouse was generated by gene targeting, and the function of GADS in T cell development and activation was examined. GADS- CD4-CD8- thymocytes exhibited a severe block in proliferation but still differentiated into mature T cells. GADS- thymocytes failed to respond to CD3 cross-linking in vivo and were impaired in positive and negative selection. Immunoprecipitation experiments revealed that the association between SLP-76 and LAT was uncoupled in GADS- thymocytes. These observations indicate that GADS is a critical adaptor for CD3 signaling.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal , Proteínas de Transporte/metabolismo , Proteínas de Membrana , Fosfoproteínas/metabolismo , Linfócitos T/citologia , Animais , Complexo CD3/metabolismo , Diferenciação Celular , Divisão Celular , Linhagem da Célula , Tamanho Celular , Feminino , Marcação de Genes , Ativação Linfocitária , Masculino , Camundongos , Camundongos Transgênicos , Fosforilação , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais , Baço/citologia , Baço/imunologia , Linfócitos T/imunologia , Timo/citologia , Timo/imunologia , Domínios de Homologia de srcRESUMO
The Ag receptor of the T lymphocyte is composed of an alphabeta heterodimer. Both alpha- and beta-chains are products of the somatic rearrangement of V(D)J segments encoded on the respective loci. During T cell development, beta-chain rearrangement precedes alpha-chain rearrangement. The mechanism of allelic exclusion ensures the expression of a single beta-chain in each T cell, whereas a large number of T cells express two functional alpha-chains. Here we demonstrate evidence that TCR alpha rearrangement is initiated by rearranging a 3' Valpha segment and a 5' Jalpha segment on both chromosomes. Rearrangement then proceeds by using upstream Valpha and downstream Jalpha segments until it is terminated by successful positive selection. This ordered and coordinated rearrangement allows a single thymocyte to sequentially express multiple TCRs with different specificities to optimize the efficiency of positive selection. Thus, the lack of allelic exclusion and TCR alpha secondary rearrangement play a key role in the formation of a functional T cell repertoire.
Assuntos
Rearranjo Gênico da Cadeia alfa dos Receptores de Antígenos dos Linfócitos T , Subpopulações de Linfócitos T/citologia , Subpopulações de Linfócitos T/metabolismo , Timo/citologia , Timo/metabolismo , Alelos , Animais , Diferenciação Celular/genética , Diferenciação Celular/imunologia , Marcadores Genéticos/imunologia , Hibridomas , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de Antígenos de Linfócitos T alfa-beta/biossíntese , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Subpopulações de Linfócitos T/imunologia , Timo/imunologia , Células Tumorais CultivadasRESUMO
While TNF-alpha is pivotal to the pathogenesis of inflammatory osteolysis, the means by which it recruits osteoclasts and promotes bone destruction are unknown. We find that a pure population of murine osteoclast precursors fails to undergo osteoclastogenesis when treated with TNF-alpha alone. In contrast, the cytokine dramatically stimulates differentiation in macrophages primed by less than one percent of the amount of RANKL (ligand for the receptor activator of NF-kappaB) required to induce osteoclast formation. Mirroring their synergistic effects on osteoclast differentiation, TNF-alpha and RANKL markedly potentiate NF-kappaB and stress-activated protein kinase/c-Jun NH(2)-terminal kinase activity, two signaling pathways essential for osteoclastogenesis. In vivo administration of TNF-alpha prompts robust osteoclast formation in chimeric animals in which ss-galactosidase positive, TNF-responsive macrophages develop within a TNF-nonresponsive stromal environment. Thus, while TNF-alpha alone does not induce osteoclastogenesis, it does so both in vitro and in vivo by directly targeting macrophages within a stromal environment that expresses permissive levels of RANKL. Given the minuscule amount of RANKL sufficient to synergize with TNF-alpha to promote osteoclastogenesis, TNF-alpha appears to be a more convenient target in arresting inflammatory osteolysis.
Assuntos
Proteínas de Transporte/farmacologia , Macrófagos/citologia , Macrófagos/efeitos dos fármacos , Glicoproteínas de Membrana/farmacologia , Osteoclastos/citologia , Osteoclastos/efeitos dos fármacos , Fator de Necrose Tumoral alfa/farmacologia , Animais , Transplante de Medula Óssea , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , Sinergismo Farmacológico , Ativação Enzimática/efeitos dos fármacos , Citometria de Fluxo , Histocitoquímica , Proteínas Quinases JNK Ativadas por Mitógeno , Macrófagos/enzimologia , Macrófagos/metabolismo , Camundongos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , NF-kappa B/metabolismo , Osteoclastos/enzimologia , Osteoclastos/metabolismo , Ligante RANK , Receptor Ativador de Fator Nuclear kappa-B , Células-Tronco/citologia , Células-Tronco/efeitos dos fármacos , Células-Tronco/enzimologia , Células-Tronco/metabolismoRESUMO
We have determined the crystal structure of I-Ag7, an integral component in murine type I diabetes development. Several features distinguish I-Ag7 from other non-autoimmune-associated MHC class II molecules, including novel peptide and heterodimer pairing interactions. The binding groove of I-Ag7 is unusual at both terminal ends, with a potentially solvent-exposed channel at the base of the P1 pocket and a widened entrance to the P9 pocket. Peptide binding studies with variants of the hen egg lysozyme I-Ag7 epitope HEL(11-25) support a comprehensive structure-based I-Ag7 binding motif. Residues critical for T cell recognition were investigated with a panel of HEL(11-25)-restricted clones, which uncovered P1 anchor-dependent structural variations. These results establish a framework for future experiments directed at understanding the role of I-Ag7 in autoimmunity.
Assuntos
Apresentação de Antígeno , Diabetes Mellitus Tipo 1/imunologia , Antígenos de Histocompatibilidade Classe II/química , Antígenos de Histocompatibilidade Classe II/metabolismo , Peptídeos/química , Peptídeos/imunologia , Sequência de Aminoácidos , Substituição de Aminoácidos/imunologia , Animais , Galinhas , Cristalografia por Raios X , Diabetes Mellitus Tipo 1/metabolismo , Dimerização , Mapeamento de Epitopos , Epitopos de Linfócito T/metabolismo , Antígenos de Histocompatibilidade Classe II/imunologia , Camundongos , Camundongos Endogâmicos NOD , Modelos Moleculares , Dados de Sequência Molecular , Muramidase/imunologia , Muramidase/metabolismo , Fragmentos de Peptídeos/imunologia , Fragmentos de Peptídeos/metabolismo , Peptídeos/metabolismo , Ligação Proteica/imunologia , Linfócitos T/imunologia , Linfócitos T/metabolismoRESUMO
Natural development of diabetes in nonobese diabetic (NOD) mice requires both CD4 and CD8 T cells. Transgenic NOD mice carrying alphabeta TCR genes from a class I MHC (Kd)-restricted, pancreatic beta cell Ag-specific T cell clone develop diabetes significantly faster than nontransgenic NOD mice. In these TCR transgenic mice, a large fraction of T cells express both transgene derived and endogenous TCR beta chains. Only T cells expressing two TCR showed reactivity to the islet Ag. Development of diabetogenic T cells is inhibited in mice with no endogenous TCR expression due to the SCID mutation. These results demonstrate that the expression of two TCRs is necessary for the autoreactive diabetogenic T cells to escape thymic negative selection in the NOD mouse. Further analysis with MHC congenic NOD mice revealed that diabetes development in the class I MHC-restricted islet Ag-specific TCR transgenic mice is still dependent on the presence of the homozygosity of the NOD MHC class II I-Ag7.
Assuntos
Linfócitos T CD8-Positivos/metabolismo , Linfócitos T CD8-Positivos/patologia , Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 1/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Timo/imunologia , Timo/metabolismo , Alelos , Animais , Autoantígenos/imunologia , Linfócitos T CD8-Positivos/imunologia , Diferenciação Celular/genética , Diferenciação Celular/imunologia , Diabetes Mellitus Tipo 1/etiologia , Diabetes Mellitus Tipo 1/patologia , Epitopos de Linfócito T/imunologia , Feminino , Regulação da Expressão Gênica/imunologia , Genes MHC da Classe II/fisiologia , Genes Codificadores da Cadeia beta de Receptores de Linfócitos T , Ilhotas Pancreáticas/imunologia , Ativação Linfocitária/genética , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Camundongos Transgênicos , Receptores de Antígenos de Linfócitos T alfa-beta/biossíntese , Timo/patologia , Transgenes/imunologiaRESUMO
Nonobese diabetic (NOD) mice carrying a segment of chromosome flanking the disrupted IFN-gamma receptor gene from original 129 ES cells are resistant to development of diabetes. However, extended backcrossing of this mouse line to the NOD mouse resulted in a segregation of the IFN-gammaR-deficient genotype from the diabetes-resistant phenotype. These results indicate that the protection of NOD mice from the development of diabetes is not directly linked to the defective IFN-gamma receptor gene but, rather, is influenced by the presence of a diabetes-resistant gene(s) closely linked to the IFN-gammaR loci derived from the 129 mouse strain.
Assuntos
Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 1/prevenção & controle , Ligação Genética/imunologia , Predisposição Genética para Doença/genética , Interferon gama , Receptores de Interferon/genética , Transferência Adotiva , Animais , Diabetes Mellitus Tipo 1/imunologia , Diabetes Mellitus Tipo 1/patologia , Feminino , Marcadores Genéticos/imunologia , Predisposição Genética para Doença/etiologia , Genótipo , Antígenos de Histocompatibilidade Classe I/biossíntese , Imunidade Inata/genética , Interferon gama/metabolismo , Interferon gama/farmacologia , Ilhotas Pancreáticas/patologia , Macrófagos Peritoneais/imunologia , Macrófagos Peritoneais/metabolismo , Camundongos , Camundongos Endogâmicos NOD , Camundongos Knockout , Receptores de Interferon/biossíntese , Receptor de Interferon gamaRESUMO
Over the last decade the concept of T cell co-stimulation has emerged to take a central role in the process of T cell activation. However, the exact definition of co-stimulation is still unclear. In this review, we re-examine the concept of co-stimulation. We suggest that while co-stimulation is important, there is little evidence to link co-stimulation with T cell anergy. We then suggest a framework for studying co-stimulation. Focusing on recent advances in our understanding of CD28, we discuss four areas of T cell activation where co-stimulation may play a role.
Assuntos
Antígenos CD28/imunologia , Ativação Linfocitária/imunologia , Transdução de Sinais/imunologia , Linfócitos T/imunologia , Animais , Sobrevivência Celular/imunologia , Humanos , Interleucina-2/genética , Interleucina-2/metabolismo , Camundongos , NF-kappa B/imunologia , Regiões Promotoras GenéticasRESUMO
Zhang, Z.-H., Chen, L., Saito, S., Kanagawa, O., and Sendo, F. 2000. Possible modulation by male sex hormone of Th1/Th2 function in protection against Plasmodium chabaudi chabaudi AS infection in mice. Experimental Parasitology 96, 121-129. We examined the mortality, survival time, and parasitemia in interferon gamma receptor (IFN-gamma R)-deficient (IFN-gamma R(-/-)) and IL-4-deficient (IL-4(-/-)) mice infected with Plasmodium chabaudi AS and compared them with the wild type counterparts (IFN-gamma R(+/+) and IL-4(+/+), respectively). (1) Mortality was higher and survival time was shorter in males of both IFN-gamma R(-/-) and IL-4(-/-) mice infected with P. chabaudi AS, compared with their wild type counterparts, whereas such a difference was not observed in female mice. (2) These differences between males and females were not observed when male mice were castrated; however, female castration had no effect on the data. (3) The rate of parasitemia in both male and female IFN-gamma R(-/-) and IL-4(-/-) mice was higher at some points during the observation than in the wild type counterparts. (4) These results on susceptibility vs resistance to P. chabaudi AS infection can be explained partially by the levels of expression of Th1/Th2 cytokine and chemokine mRNAs in the spleen cells of the infected mice. These results suggest that male sex hormones modulate the function of Th1/Th2 cells and that these T cells counteract the activity of these hormones in protection against P. chabaudi AS infection in mice.
Assuntos
Malária/imunologia , Plasmodium chabaudi/imunologia , Testosterona/fisiologia , Células Th1/imunologia , Células Th2/imunologia , Animais , Castração , Quimiocinas/genética , Quimiocinas/metabolismo , Citocinas/genética , Citocinas/metabolismo , Feminino , Expressão Gênica , Interleucina-4/genética , Interleucina-4/fisiologia , Malária/mortalidade , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Parasitemia/imunologia , Parasitemia/mortalidade , RNA Mensageiro/metabolismo , Receptores de Interferon/genética , Receptores de Interferon/fisiologia , Fatores Sexuais , Organismos Livres de Patógenos Específicos , Baço/imunologia , Fatores de Tempo , Receptor de Interferon gamaRESUMO
Mice expressing hen egg-white lysozyme (HEL) as a transgene are unresponsive to immunization with the HEL protein. Profound tolerance was found even in situations where the amounts of l-A(k)-peptide complexes was 100 or less per APC. Among the few T cells that escaped tolerance, we did not observe differential responses to the different HEL epitopes, perhaps because of the very high sensitivity of the negative selection process. The same HEL transgenic mice that did not respond to HEL responded to immunization with the 46-61 peptide of HEL. These peptide-specific T cells that escaped negative selection belonged to a set that reacted with a particular conformer of the HEL peptide-l-A(k) (type B). The presence of type B reactive T cells should be considered in autoimmunity.
Assuntos
Deleção Clonal , Epitopos/imunologia , Antígenos de Histocompatibilidade Classe II/imunologia , Tolerância Imunológica/imunologia , Contagem de Linfócitos , Muramidase/imunologia , Fragmentos de Peptídeos/imunologia , Subpopulações de Linfócitos T/imunologia , Sequência de Aminoácidos , Animais , Apresentação de Antígeno , Galinhas/imunologia , Imunização , Camundongos , Camundongos Transgênicos , Dados de Sequência Molecular , Muramidase/genética , Fragmentos de Peptídeos/genéticaRESUMO
CD2-associated protein (CD2AP) is an 80-kilodalton protein that is critical for stabilizing contacts between T cells and antigen-presenting cells. In CD2AP-deficient mice, immune function was compromised, but the mice died at 6 to 7 weeks of age from renal failure. In the kidney, CD2AP was expressed primarily in glomerular epithelial cells. Knockout mice exhibited defects in epithelial cell foot processes, accompanied by mesangial cell hyperplasia and extracellular matrix deposition. Supporting a role for CD2AP in the specialized cell junction known as the slit diaphragm, CD2AP associated with nephrin, the primary component of the slit diaphragm.
Assuntos
Glomérulos Renais/metabolismo , Glomérulos Renais/ultraestrutura , Síndrome Nefrótica/congênito , Proteínas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Animais , Membrana Basal/ultraestrutura , Proteínas do Citoesqueleto , Células Epiteliais/metabolismo , Células Epiteliais/ultraestrutura , Proteínas da Matriz Extracelular/metabolismo , Mesângio Glomerular/metabolismo , Mesângio Glomerular/ultraestrutura , Junções Intercelulares/metabolismo , Junções Intercelulares/ultraestrutura , Glomérulos Renais/irrigação sanguínea , Ativação Linfocitária , Proteínas de Membrana , Camundongos , Camundongos Knockout , Microscopia Eletrônica , Síndrome Nefrótica/genética , Síndrome Nefrótica/metabolismo , Síndrome Nefrótica/patologia , Proteínas/genética , Proteínas Recombinantes de Fusão/metabolismo , Linfócitos T/imunologiaRESUMO
Mice carrying a transgenic TCR with targeted disruption of the TCR alpha chain (H-Y alpha(-/-)) possess CD4(+) T cells which express the transgenic TCR beta without the alpha chain. These mice developed the murine acquired immunodeficiency syndrome (MAIDS) after infection with LP-BM5 retroviruses, a process which requires CD4(+) T cells. These cells are negative for TCR delta chain and pre-TCR alpha chain expression, and thus express a unique surface receptor with the TCR beta chain as a component. The cells respond to MAIDS virus-associated superantigen and concanavalin A, but not to protein antigens such as ovalbumin. Thus, this novel surface receptor appears to play an important role in the pathogenesis of MAIDS.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Síndrome de Imunodeficiência Adquirida Murina/imunologia , Receptores de Antígenos de Linfócitos T/fisiologia , Animais , Linfócitos T CD8-Positivos/imunologia , Diferenciação Celular , Células Cultivadas , Feminino , Genes RAG-1/genética , Hibridomas/imunologia , Contagem de Linfócitos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/metabolismo , RetroviridaeRESUMO
We discuss here the problems in identifying sequence motifs of peptides that bind to I-A(g7), the class II histocompatibility molecule of NOD diabetic mice. We present studies that indicate a minor contribution of amino acid side chains for binding. A peptide from the Ealpha chain binds to I-A(g7) molecules and is recognized by CD4 T cells. By producing single-residue mutations we identified four residues that were considered to contact the T cell receptor. No residue was found to be essential for binding to I-A(g7): a peptide that contained the T cell contact residues, on a backbone of alanines, bound to I-A(g7) and stimulated the T cells. We conclude that peptides can bind to I-A(g7) without the requirement for residues with prominent side chains to anchor them.
Assuntos
Antígenos de Histocompatibilidade Classe II/imunologia , Peptídeos/imunologia , Animais , Antígenos de Superfície/genética , Antígenos de Superfície/imunologia , Ligação Competitiva/imunologia , Linfócitos T CD4-Positivos/imunologia , Hibridomas/imunologia , Camundongos , Camundongos Endogâmicos NOD , Mutação , Ovalbumina/imunologia , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/imunologia , Ligação Proteica/imunologia , Receptores de Antígenos de Linfócitos T/imunologiaRESUMO
We quantitated the number of peptide-class II MHC complexes required to affect the deletion or activation of 3A9 TCR transgenic thymocytes. Deletion of immature double positive thymocytes was very sensitive, taking place with approximately three peptide-MHC complexes per APC. However, the activation of mature CD4+ thymocytes required 100-fold more complexes per APC. Therefore, a "biochemical margin of safety" exists at the level of the APC. To be activated, autoreactive T cells in peripheral lymphoid tissues require a relatively high level of peptide-MHC complexes.
Assuntos
Antígenos de Histocompatibilidade Classe II/imunologia , Peptídeos/imunologia , Subpopulações de Linfócitos T/imunologia , Timo/imunologia , Animais , Células Apresentadoras de Antígenos/metabolismo , Antígenos CD/biossíntese , Antígenos de Diferenciação de Linfócitos T/biossíntese , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Diferenciação Celular/imunologia , Deleção Clonal , Antígenos de Histocompatibilidade Classe II/metabolismo , Lectinas Tipo C , Substâncias Macromoleculares , Camundongos , Camundongos Endogâmicos C57BL , Peptídeos/metabolismo , Subpopulações de Linfócitos T/metabolismo , Timo/citologia , Timo/metabolismo , Regulação para Cima/imunologiaRESUMO
We examined the role of the peptide/MHC ligand in CD4+ T cell differentiation into Th1 or Th2 cells using a TCR alphabeta transgenic mouse specific for hemoglobin (Hb)(64-76)/I-Ek. We identified two altered peptide ligands of Hb(64-76) that retain strong agonist activity but, at a given dose, induce cytokine patterns distinct from the Hb(64-76) peptide. The ability of these peptides to produce distinct cytokine patterns at identical doses is not due to an intrinsic qualitative property. Each peptide can induce Th2 cytokines at low concentrations and Th1 cytokines at high concentrations and has a unique range of concentrations at which these distinct effects occur. The pattern of cytokines produced from limiting dilution of naive T cells demonstrated that the potential to develop an individual Th1 or Th2 cell is stochastic, independent of Ag dose. We propose that the basis for the observed effects on the Th1/Th2 balance shown by the altered peptide ligands and the amount of Ag dose involves the modification of soluble factors in bulk cultures that are the driving force that polarize the population to either a Th1 or Th2 phenotype.
Assuntos
Antígenos/imunologia , Hemoglobinas/imunologia , Fragmentos de Peptídeos/imunologia , Peptídeos/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/fisiologia , Linfócitos T Auxiliares-Indutores/imunologia , Animais , Antígenos/genética , Diferenciação Celular/genética , Diferenciação Celular/imunologia , Linhagem Celular , Citocinas/biossíntese , Relação Dose-Resposta Imunológica , Genes RAG-1/imunologia , Antígenos H-2/genética , Haplótipos , Hemoglobinas/genética , Interferon gama/antagonistas & inibidores , Interferon gama/biossíntese , Interferon gama/farmacologia , Interleucina-4/biossíntese , Ligantes , Camundongos , Camundongos Endogâmicos AKR , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fragmentos de Peptídeos/genética , Peptídeos/metabolismo , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Baço/citologia , Linfócitos T/imunologia , Linfócitos T/metabolismo , Linfócitos T Auxiliares-Indutores/citologia , Linfócitos T Auxiliares-Indutores/metabolismo , Células Th1/citologia , Células Th2/citologiaRESUMO
The diabetes-susceptible class II MHC genes (in human and mouse) share unique nonaspartic acid residues at position 57 of the class II beta-chain. Transgenic expression of a mutant I-A(g7), substituting histidine and serine at position 56 and 57 of beta-chain with proline and aspartic acid (I-A(g7)PD), respectively, inhibits diabetes development in the nonobese diabetic mouse model. Here, we demonstrate that immature thymocytes expressing a diabetogenic islet Ag-specific transgenic TCR are positively selected by I-A(g7)PD class II MHC to give rise to mature CD4+ T cells. However, splenic APCs expressing the same I-A(g7)PD fail to present pancreatic islet Ag to mature T cells bearing this diabetogenic TCR. These results indicate that nonaspartic acid residues at position 57 of class II MHC beta-chain is important for diabetogenic CD4+ T cell activation in the periphery but is not essential for the formation of a diabetogenic T cell repertoire in the thymus.
Assuntos
Doenças Autoimunes/imunologia , Linfócitos T CD4-Positivos/imunologia , Deleção Clonal , Diabetes Mellitus Tipo 1/imunologia , Antígenos de Histocompatibilidade Classe II/genética , Ilhotas Pancreáticas/imunologia , Ativação Linfocitária , Linfócitos T Citotóxicos/imunologia , Timo/imunologia , Substituição de Aminoácidos , Animais , Apresentação de Antígeno , Códon/genética , DNA Complementar/genética , Antígenos de Histocompatibilidade Classe II/imunologia , Ilhotas Pancreáticas/patologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos NOD , Camundongos SCID , Camundongos Transgênicos , Mutação Puntual , Regiões Promotoras Genéticas , Quimera por Radiação , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/imunologia , Organismos Livres de Patógenos Específicos , Baço/patologia , Linfócitos T Citotóxicos/patologia , Timo/patologiaRESUMO
Mice infected with murine acquired immunodeficiency syndrome (MAIDS) virus developed lymphoadenopathy and profound immunodeficiency. Concomitantly the expression of endogenous mammary tumor virus (MTV) mRNA increased significantly, especially for the 1.7-kb 3' open reading frame (ORF) mRNA encoding MTV superantigen. B cell lines that are established from MAIDS mice and exhibit superantigen activity also express a high level of 1.7-kb endogenous MTV and mRNA. Infection of a B cell tumor line in vitro with retrovirus containing the cloned MAIDS virus gene induced superantigen activity and this cell line also expressed the 1.7-kb superantigen coding MTV 3' ORF mRNA. These results strongly suggest a link between MAIDS virus infection and the induction of endogenous superantigen activity. This may play an important role in the pathogenesis of the MAIDS virus.