RESUMO
Sepsis is a complex condition of inflammatory and immune dysregulation, triggered by severe infection. In survivors, chronic inflammation and immune dysregulation linger, facilitating the emergence of infections. CD8 dysfunction contributes to immunosuppression in sepsis survivors. We devised an animal model that enabled us to identify and analyze CD8-intrinsic defects induced by sepsis. We adoptively transferred CD45.1 CD8 OT-I T cells into CD45.2 congenic mice and subjected them to cecal ligature and puncture, to induce abdominal sepsis. One month later, we isolated the transferred CD8 cells. Surface marker expression confirmed they had not been activated through the TCR. CD8 OT-I T cells isolated from septic (or sham-operated) mice were transferred to second recipients, which were challenged with OVA-expressing Listeria monocytogenes. We compared effector capacities between OT-I cells exposed to sepsis and control cells. Naive mice that received OT-I cells exposed to sepsis had higher bacterial burden and a shorter survival when challenged with OVA-expressing L. monocytogenes. OT-I cells isolated from septic mice produced less IFN-γ but had conserved activation, expansion potential, and cytotoxic function. We observed lower transcript levels of IFN-γ and of the long noncoding RNA Ifng-as1, a local regulator of the epigenetic landscape, in cells exposed to sepsis. Accordingly, local abundance of a histone modification characteristic of active promoter regions was reduced in sepsis-exposed CD8 T cells. Our results identify a mechanism through which inflammation in the context of sepsis affects CD8 T cell function intrinsically.
Assuntos
Linfócitos T CD8-Positivos , Cromatina , Interferon gama , Listeria monocytogenes , Sepse , Animais , Camundongos , Transferência Adotiva , Linfócitos T CD8-Positivos/imunologia , Cromatina/imunologia , Cromatina/metabolismo , Modelos Animais de Doenças , Interferon gama/imunologia , Listeria monocytogenes/imunologia , Listeriose/imunologia , Ativação Linfocitária/imunologia , Camundongos Endogâmicos C57BL , Sepse/imunologiaRESUMO
OBJECTIVE: Variants in STAT4 are associated with systemic lupus erythematosus (SLE) and other autoimmune diseases. We undertook this study to investigate how disease-associated variants affect STAT4 expression, in particular in CD4+ T cells where STAT4 plays an essential role. METHODS: We compared Th1 differentiation between naive CD4+ T cells from healthy donors homozygous for the risk (R/R) or nonrisk (NR/NR) alleles. We analyzed epigenetic marks in STAT4 and evaluated the relevance of its third intron, assessed the consequences of Stat4 overexpression in vivo in mice, and analyzed the effects of the STAT4 genotype in patients with lupus nephritis. RESULTS: Naive CD4+ T cells from NR/NR healthy donors down-regulated STAT4 in response to interleukin-12 (IL-12). In contrast, cells from R/R healthy donors maintained high levels. R/R cells exhibited a higher abundance of transcriptionally active STAT4 and increased interferon-γ production. Accordingly, R/R healthy donors exhibited a stronger induction of local active enhancer marks. Genetic editing confirmed the presence of a negative regulatory region in the STAT4 third intron, where most of the SLE-associated STAT4 single-nucleotide polymorphisms (SNPs) are located. In vivo forced expression demonstrated that increases in Stat4 levels in T cells enhanced glomerulonephritis in mice. Accordingly, the R/R genotype was associated with suboptimal response to treatment and with worse clinical outcomes in patients with proliferative lupus nephritis. CONCLUSION: The SLE-associated STAT4 haplotype correlates with an abnormal IL-12-mediated STAT4 transcriptional regulation. Carriers of the risk variant exhibit exaggerated CD4+ proinflammatory capacities that, in the context of SLE, contribute to more severe disease. R/R patients may benefit from blockade of the IL-12/STAT4 pathway.
Assuntos
Lúpus Eritematoso Sistêmico , Nefrite Lúpica , Animais , Camundongos , Linfócitos T CD4-Positivos/metabolismo , Regulação para Baixo , Haplótipos , Interferon gama/genética , Interleucina-12 , Lúpus Eritematoso Sistêmico/genética , Nefrite Lúpica/genética , Polimorfismo de Nucleotídeo Único , Fator de Transcrição STAT4/genética , HumanosRESUMO
Cryptocurrency markets have attracted many interest for global investors because of their novelty, wide on-line availability, increasing capitalization, and potential profits. In the econophysics tradition, we show that many of the most available cryptocurrencies have return statistics that do not follow Gaussian distributions, instead following heavy-tailed distributions. Entropy measures are applied, showing that portfolio diversification is a reasonable practice for decreasing return uncertainty.
RESUMO
Adaptive immune responses rely on the proliferation of T lymphocytes able to recognize and eliminate pathogens. The magnitude and duration of the expansion of activated T cell clones are finely regulated to minimize immunopathology and avoid autoimmunity. In patients with rheumatic autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis, activated lymphocytes survive and exert effector functions for prolonged periods, defying the mechanisms that normally curb their capacities during acute and chronic infections. Here, we review the molecular mechanisms that limit the duration of immune responses in health and discuss the factors that alter such regulation in the setting of systemic lupus erythematosus and rheumatoid arthritis. We highlight defects that could contribute to the development and progression of autoimmune disease and describe how chronic inflammation can alter the regulation of activated lymphocyte survival, promoting its perpetuation. These concepts might contribute to the understanding of the mechanisms that underlie the chronicity of inflammation in the context of autoimmunity.
Assuntos
Artrite Reumatoide , Doenças Autoimunes , Lúpus Eritematoso Sistêmico , Doenças Reumáticas , Autoimunidade , Sobrevivência Celular , Humanos , Inflamação , Linfócitos TRESUMO
Activation of self-reactive CD8+ T cells induces a peripheral tolerance mechanism that involves loss of CD8 expression. Because genetic deficiency of Fas and Fasl causes the accumulation of double-negative (DN; CD3+ TCR-αß+ CD4- CD8-) T cells that have been proposed to derive from CD8+ cells, we decided to explore the role of Fas and FasL in self-antigen-induced CD8 downregulation. To this end, we quantified Fas and FasL induction by different stimuli and analyzed the effects of Fas/FasL deficiency during a protective immune response and after exposure to self-antigens. Our data describes how Fas and FasL upregulation differs depending on the setting of CD8 T cell activation and demonstrates that Fas/FasL signaling maintains CD8 expression during repetitive antigen stimulation and following self-antigen encounter. Together, our results reveal an unexpected role of Fas/FasL signaling and offer a new insight into the role of these molecules in the regulation of immune tolerance.
Assuntos
Autoantígenos/metabolismo , Antígenos CD8/metabolismo , Linfócitos T CD8-Positivos/metabolismo , Proteína Ligante Fas/metabolismo , Tolerância Imunológica , Ativação Linfocitária , Receptor fas/metabolismo , Transferência Adotiva , Animais , Autoantígenos/imunologia , Antígenos CD8/imunologia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/transplante , Células Cultivadas , Regulação para Baixo , Proteína Ligante Fas/genética , Proteína Ligante Fas/imunologia , Cinética , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fenótipo , Transdução de Sinais , Receptor fas/genética , Receptor fas/imunologiaRESUMO
How T cells integrate environmental cues into signals that limit the magnitude and length of immune responses is poorly understood. Here, we provide data that demonstrate that B55ß, a regulatory subunit of protein phosphatase 2A, represents a molecular link between cytokine concentration and apoptosis in activated CD8+ T cells. Through the modulation of AKT, B55ß induced the expression of the proapoptotic molecule Hrk in response to cytokine withdrawal. Accordingly, B55ß and Hrk were both required for in vivo and in vitro contraction of activated CD8+ lymphocytes. We show that this process plays a role during clonal contraction, establishment of immune memory, and preservation of peripheral tolerance. This regulatory pathway may represent an unexplored opportunity to end unwanted immune responses or to promote immune memory.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Memória Imunológica , Proteína Fosfatase 2/imunologia , Animais , Proteínas Reguladoras de Apoptose/genética , Proteínas Reguladoras de Apoptose/imunologia , Camundongos , Camundongos Transgênicos , Neuropeptídeos/genética , Neuropeptídeos/imunologia , Proteína Fosfatase 2/genética , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/imunologiaRESUMO
CD8 T cells can kill malignant cells in an antigen-specific manner. However, anti-tumoral responses are usually limited by suppressive factors that curb the effector responses of tumor-infiltrating CD8 T cells. Therapeutic strategies to overcome intra-tumoral T cell suppression, for example immune checkpoint inhibition, have been clinically effective in patients with cancer. Here, we provide data that demonstrates that GK-1, a peptide derived from the parasite Taenia crassiceps, promotes an anti-melanoma CD8 T cell response with heightened effector characteristics that leads to an increased amount of tumor-infiltrating CD44+ IFN-γ-producing CD8 T cells. The response induced by GK-1 was associated with a reduction in the expression of PD-1 and PD-L1 on tumor-infiltrating CD8 and dendritic cells, respectively, effects that led to a dramatic decrease in tumor burden. Our results suggest that the immunomodulatory properties of GK-1 may promote a CD8 T cell response that may be therapeutically useful in the setting of cancer.