RESUMO
Foxp3(+) regulatory T (Treg) cells limit inflammatory responses and maintain immune homeostasis. Although comprised of several phenotypically and functionally distinct subsets, the differentiation of specialized Treg cell populations within the periphery is poorly characterized. We demonstrate that the development of T-bet(+) Treg cells that potently inhibit T helper 1 (Th1) cell responses was dependent on the transcription factor STAT1 and occurred directly in response to interferon-γ produced by effector T cells. Additionally, delayed induction of the IL-12Rß2 receptor component after STAT1 activation helped ensure that Treg cells do not readily complete STAT4-dependent Th1 cell development and lose their ability to suppress effector T cell proliferation. Thus, we define a pathway of abortive Th1 cell development that results in the specialization of peripheral Treg cells and demonstrate that impaired expression of a single cytokine receptor helps maintain Treg cell-suppressive function in the context of inflammatory Th1 cell responses.
Assuntos
Diferenciação Celular , Subunidade beta 2 de Receptor de Interleucina-12/imunologia , Linfócitos T Reguladores/imunologia , Células Th1/imunologia , Animais , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Citometria de Fluxo , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/imunologia , Fatores de Transcrição Forkhead/metabolismo , Interferon gama/genética , Interferon gama/metabolismo , Interferon gama/farmacologia , Interleucina-12/farmacologia , Subunidade beta 2 de Receptor de Interleucina-12/genética , Subunidade beta 2 de Receptor de Interleucina-12/metabolismo , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Receptores CXCR3/genética , Receptores CXCR3/imunologia , Receptores CXCR3/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Transcrição STAT1/genética , Fator de Transcrição STAT1/imunologia , Fator de Transcrição STAT1/metabolismo , Fator de Transcrição STAT4/imunologia , Fator de Transcrição STAT4/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/imunologia , Proteínas com Domínio T/genética , Proteínas com Domínio T/imunologia , Proteínas com Domínio T/metabolismo , Linfócitos T Reguladores/metabolismo , Células Th1/metabolismo , Fatores de TempoRESUMO
BACKGROUND: There are a lack of biomarkers which can be used to predict clinical outcomes for multiple sclerosis (MS) patients receiving interferon beta (IFN-ß). Thus the objective of this study was to characterize changes in CD4+ T-lymphocyte expression in an unbiased manner following initiation of intramuscular (IM) IFN-ß-1a treatment, and then to verify those findings using marker-specific assays. METHODS: Peripheral blood specimens were collected from twenty MS patients before and after treatment with intramuscular (IM) IFN-ß-1a and were used for isolation of mononuclear cells (PBMCs). mRNA expression patterns of negatively-selected CD4+ T-cells from the PBMCs were analyzed using microarray gene expression technology. IL-12 and IL-23 receptor levels on PBMC-derived CD4+ T-cells were analyzed by flow cytometry. The phosphorylation status of Stat4 was measured by performing densitometry on western blots. RESULTS: Microarray analyses demonstrated that mRNA expression of the IL-12Rß2 gene was uniformly up-regulated in response to IFN-ß-1a treatment and was associated with an increased number of IL-12Rß2+ CD4+ T-cells by flow cytometry in 4 of 6 patients. This finding was substantiated by demonstrating that Stat4 phosphorylation, a transcription factor for IL-12, was increased after treatment. Conversely, the number of IL-23R+ CD4+ T-cells was decreased following treatment. CONCLUSIONS: The IL-12 receptor shares a common subunit, the IL-12Rß2, with the IL-23 receptor. Both of these receptors have a probable role in regulating IL-17 and TH-17 cells, important mediators of inflammation in multiple sclerosis (MS). Thus, the changes in the numbers of CD4+ T-cells expressing these receptors in response to IFN-ß-1a treatment may point to an important mechanism of action for this drug, but further large scale studies are needed to confirm these preliminary observations.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Interferon beta/administração & dosagem , Subunidade beta 2 de Receptor de Interleucina-12/efeitos dos fármacos , Esclerose Múltipla Recidivante-Remitente/tratamento farmacológico , Esclerose Múltipla Recidivante-Remitente/imunologia , Receptores de Interleucina-12/efeitos dos fármacos , Receptores de Interleucina/efeitos dos fármacos , Adjuvantes Imunológicos/uso terapêutico , Adulto , Contagem de Linfócito CD4 , Feminino , Expressão Gênica/efeitos dos fármacos , Humanos , Injeções Intramusculares , Interferon beta-1a , Subunidade beta 2 de Receptor de Interleucina-12/imunologia , Ativação Linfocitária/efeitos dos fármacos , Ativação Linfocitária/genética , Masculino , Pessoa de Meia-Idade , Receptores de Interleucina/imunologia , Receptores de Interleucina-12/imunologiaRESUMO
The generation of reactive oxygen species (ROS) is inherent to immune responses. ROS are crucially involved in host defense against pathogens by promoting bacterial killing, but also as signaling agents coordinating the production of cytokines. Transient Receptor Potential Melastatin 2 (TRPM2) is a Ca(2+)-permeable channel gated via binding of ADP-ribose, a metabolite formed under conditions of cellular exposure to ROS. Here, we show that TRPM2-deficient mice are extremely susceptible to infection with Listeria monocytogenes (Lm), exhibiting an inefficient innate immune response. In a comparison with IFNγR-deficient mice, TRPM2(-/-) mice shared similar features of uncontrolled bacterial replication and reduced levels of inducible (i)NOS-expressing monocytes, but had intact IFNγ responsiveness. In contrast, we found that levels of cytokines IL-12 and IFNγ were diminished in TRPM2(-/-) mice following Lm infection, which correlated with their reduced innate activation. Moreover, TRPM2(-/-) mice displayed a higher degree of susceptibility than IL-12-unresponsive mice, and supplementation with recombinant IFNγ was sufficient to reverse the unrestrained bacterial growth and ultimately the lethal phenotype of Lm-infected TRPM2(-/-) mice. The severity of listeriosis we observed in TRPM2(-/-) mice has not been reported for any other ion channel. These findings establish an unsuspected role for ADP-ribose and ROS-mediated cation flux for innate immunity, opening up unique possibilities for immunomodulatory intervention through TRPM2.