RESUMEN
Human blood CD14+ monocytes are bone marrow-derived white blood cells that sense and respond to pathogens. Although innate immune activation by RNA viruses preferentially occurs through intracellular RIG-I-like receptors, other nucleic acid recognition receptors, such as Toll-like receptors (TLRs), play a role in finely programming the final outcome of virus infection. Here, we dissected how human monocytes respond to infection with either Coxsackie (CV), encephalomyocarditis (EMCV), influenza A (IAV), measles (MV), Sendai (SV), or vesicular stomatitis (VSV) virus. We found that in monocytes, type I interferon (IFN) and cytokine responses to infection were RNA virus specific and differentially involved TLR7 and TLR8, which sense single-stranded RNA. These TLRs activated distinct signaling cascades in monocytes, which correlated with differences in the production of cytokines involved in the polarization of CD4+ T helper cells. Furthermore, we found that TLR7 signaling specifically increased expression of the transcription factor FOSL1, which reduced IL-27 and TNFα production by monocytes. TLR7, but not TLR8, activation of monocytes also stimulated Ca2+ flux that prevented type I IFN responses. Our work demonstrates that in human monocytes, TLR7 and TLR8 triggered different signaling pathways that contribute to distinct phenotypes during RNA virus infection. In addition, we defined individual targets within these pathways that promoted specific T helper and antiviral responses.
Asunto(s)
Monocitos/inmunología , Virus ARN/inmunología , Transducción de Señal/inmunología , Receptor Toll-Like 7/inmunología , Receptor Toll-Like 8/inmunología , Calcio/inmunología , Calcio/metabolismo , Células Cultivadas , Citocinas/genética , Citocinas/inmunología , Citocinas/metabolismo , Regulación de la Expresión Génica/inmunología , Interacciones Huésped-Patógeno/inmunología , Humanos , Interferón Tipo I/genética , Interferón Tipo I/inmunología , Interferón Tipo I/metabolismo , Monocitos/metabolismo , Monocitos/virología , Proteínas Proto-Oncogénicas c-fos/genética , Proteínas Proto-Oncogénicas c-fos/inmunología , Proteínas Proto-Oncogénicas c-fos/metabolismo , Interferencia de ARN , Virus ARN/clasificación , Virus ARN/fisiología , Transducción de Señal/genética , Receptor Toll-Like 7/genética , Receptor Toll-Like 7/metabolismo , Receptor Toll-Like 8/genética , Receptor Toll-Like 8/metabolismoRESUMEN
Foxp3(+) regulatory T cells (Tregs) exhibit plasticity, which dictates their function. Secretion of the inflammatory cytokine IFNγ, together with the acquisition of a T helper 1 (Th1)-like effector phenotype as observed in cancer, infection, and autoimmune diseases, is associated with loss of Treg suppressor function through an unknown mechanism. Here, we describe the signaling events driving the generation of human Th1-Tregs. Using a genome-wide gene expression approach and pathway analysis, we identify the PI3K/AKT/Foxo1/3 signaling cascade as the major pathway involved in IFNγ secretion by human Tregs. Furthermore, we describe the opposing roles of AKT isoforms in Th1-Treg generation ex vivo Finally, we employ multiple sclerosis as an in vivo model with increased but functionally defective Th1-Tregs. We show that the PI3K/AKT/Foxo1/3 pathway is activated in ex vivo-isolated Tregs from untreated relapsing-remitting MS patients and that blockade of the pathway inhibits IFNγ secretion and restores the immune suppressive function of Tregs. These data define a fundamental pathway regulating the function of human Tregs and suggest a novel treatment paradigm for autoimmune diseases.
Asunto(s)
Enfermedades Autoinmunes/inmunología , Enfermedades Autoinmunes/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Linfocitos T Reguladores/inmunología , Linfocitos T Reguladores/metabolismo , Enfermedades Autoinmunes/genética , Biomarcadores , Diferenciación Celular , Citocinas , Factores de Transcripción Forkhead/metabolismo , Perfilación de la Expresión Génica , Silenciador del Gen , Humanos , Inmunomodulación , Interferón gamma/metabolismo , Fenotipo , Fosfatidilinositol 3-Quinasas/metabolismo , Isoformas de Proteínas , Transducción de Señal , Subgrupos de Linfocitos T/inmunología , Subgrupos de Linfocitos T/metabolismo , Linfocitos T Reguladores/citología , TranscriptomaRESUMEN
The recognition of microbial patterns by Toll-like receptors (TLRs) is critical for activation of the innate immune system. Although TLRs are expressed by human CD4(+) T cells, their function is not well understood. Here we found that engagement of TLR7 in CD4(+) T cells induced intracellular calcium flux with activation of an anergic gene-expression program dependent on the transcription factor NFATc2, as well as unresponsiveness of T cells. As chronic infection with RNA viruses such as human immunodeficiency virus type 1 (HIV-1) induces profound dysfunction of CD4(+) T cells, we investigated the role of TLR7-induced anergy in HIV-1 infection. Silencing of TLR7 markedly decreased the frequency of HIV-1-infected CD4(+) T cells and restored the responsiveness of those HIV-1(+) CD4(+) T cells. Our results elucidate a previously unknown function for microbial pattern-recognition receptors in the downregulation of immune responses.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Infecciones por VIH/inmunología , VIH-1/inmunología , Receptor Toll-Like 7/inmunología , Linfocitos T CD4-Positivos/virología , Calcio/inmunología , Anergia Clonal/inmunología , Regulación hacia Abajo , Infecciones por VIH/virología , Humanos , Leucocitos Mononucleares/inmunología , Activación de Linfocitos , Factores de Transcripción NFATC/inmunología , ARN Interferente Pequeño/administración & dosificación , ARN Interferente Pequeño/genética , Receptor Toll-Like 7/antagonistas & inhibidores , Receptor Toll-Like 7/genéticaRESUMEN
T-cell immunoglobulin and mucin domain 3 (TIM-3) is an Ig-superfamily member expressed on IFN-γ-secreting Th1 and Tc1 cells and was identified as a negative regulator of immune tolerance. TIM-3 is expressed by a subset of activated CD4(+) T cells, and anti-CD3/anti-CD28 stimulation increases both the level of expression and the number of TIM-3(+) T cells. In mice, TIM-3 is constitutively expressed on natural regulatory T (Treg) cells and has been identified as a regulatory molecule of alloimmunity through its ability to modulate CD4(+) T-cell differentiation. Here, we examined TIM-3 expression on human Treg cells to determine its role in T-cell suppression. In contrast to mice, TIM-3 is not expressed on Treg cells ex vivo but is upregulated after activation. While TIM-3(+) Treg cells with increased gene expression of LAG3, CTLA4, and FOXP3 are highly efficient suppressors of effector T (Teff) cells, TIM-3(-) Treg cells poorly suppressed Th17 cells as compared with their suppression of Th1 cells; this decreased suppression ability was associated with decreased STAT-3 expression and phosphorylation and reduced gene expression of IL10, EBI3, GZMB, PRF1, IL1Rα, and CCR6. Thus, our results suggest that TIM-3 expression on Treg cells identifies a population highly effective in inhibiting pathogenic Th1- and Th17-cell responses.