RESUMEN
The binding of programmed death 1 (PD-1) to its ligands PD-L1 and PD-L2 on antigen-presenting cells turns off autoreactive T cells and induces peripheral tolerance. Aberrant PD-1/PD-L signalling could result in a breakdown of peripheral tolerance and lead to autoimmune diseases. In this study, we detected PD-1 and PD-L expression on T cells and dendritic cells (DCs) in immune thrombocytopenia (ITP) patients with active disease by flow cytometry. The effects of PD-L1-Fc fusion protein (PD-L1-Fc) on T cells and on secretion of interferon-γ (IFN-γ) and interleukin-2 (IL-2) were detected by flow cytometry and enzyme-linked immunosorbent assay, respectively. Compared with healthy controls, PD-1 expression was significantly increased in CD4+ T cells and CD8+ T cells from patients with active ITP. However, PD-L1 expression on monocyte-derived DCs was lower in patients with active ITP than in healthy controls. In vitro assays revealed that PD-L1-Fc increased T cell apoptosis, inhibited activation and proliferation of CD4+ T cells and CD8+ T cells and decreased IFN-γ and IL-2 secretion in patients with active ITP. These results suggest that the aberrant PD-1/PD-L negative co-stimulatory pathway may play a role in ITP. Enhancing PD-1/PD-L signalling might be a promising therapeutic approach for ITP patients by enhancing T cell apoptosis, inhibiting T cell activation and proliferation and reducing secretion of inflammatory factors.
Asunto(s)
Antígeno B7-H1/metabolismo , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Receptor de Muerte Celular Programada 1/metabolismo , Púrpura Trombocitopénica Idiopática/metabolismo , Adolescente , Adulto , Anciano , Apoptosis , Antígeno B7-H1/genética , Proliferación Celular , Células Cultivadas , Femenino , Humanos , Activación de Linfocitos/efectos de los fármacos , Masculino , Persona de Mediana Edad , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/farmacología , Transducción de Señal , Regulación hacia Arriba , Adulto JovenRESUMEN
Thalidomide (THD) is an immunomodulatory agent used to treat immune-mediated diseases. Immune thrombocytopenia (ITP) is an autoimmune disorder in which impaired mesenchymal stem cells (MSCs) are potentially involved. We demonstrated that MSCs in ITP patients had reduced proliferative capacity and lost their immunosuppressive function, which could be corrected with THD treatment. According to the gene profile, the downregulation of caspase-8 and caspase-10, and upregulation of oct3/4 and tgf-ß1, may be associated with THD modulation. Dendritic cells (DCs) played an important role in mediating the inhibitory activity of MSCs. To study the functional alteration of DCs elicited by MSCs, we sorted DCs after incubation with MSCs and performed T-lymphocyte reaction assays. The THD-modulated MSCs from ITP patients induced mature DCs to become tolerogenic DCs, whereas unmodulated MSCs had no effect. The induction of tolerogenicity in DCs by MSCs was dependent on the expression of TIEG1 in DCs. The study reveals the inability of MSCs from ITP patients to induce tolerogenic ability in DCs. THD could restore the regulatory effect of MSCs on DCs. These findings will help us understand the pathogenesis of ITP, and with appropriate safeguards, THD may benefit patients with ITP.
Asunto(s)
Células Dendríticas/inmunología , Tolerancia Inmunológica/efectos de los fármacos , Inmunosupresores/farmacología , Células Madre Mesenquimatosas/metabolismo , Púrpura Trombocitopénica Idiopática/inmunología , Púrpura Trombocitopénica Idiopática/metabolismo , Talidomida/farmacología , Adolescente , Adulto , Anciano , Estudios de Casos y Controles , Proliferación Celular/efectos de los fármacos , Factores de Transcripción de la Respuesta de Crecimiento Precoz/genética , Factores de Transcripción de la Respuesta de Crecimiento Precoz/metabolismo , Femenino , Perfilación de la Expresión Génica , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , Masculino , Persona de Mediana Edad , Púrpura Trombocitopénica Idiopática/genética , Interferencia de ARN , Adulto JovenRESUMEN
INTRODUCTION: Indoleamine 2,3-dioxygenase (IDO) can promote peripheral immune tolerance and control autoimmune responses through tryptophan catabolism. Tryptophanyl-tRNA synthetase (TTS) can protect T cells from IDO-mediated cell injury. Impaired IDO-mediated tryptophan catabolism has been observed in some autoimmune diseases. MATERIALS AND METHODS: The concentrations of plasma kynurenine and tryptophan were detected by high-pressure liquid chromatography. The expressions of IDO and TTS were analyzed by real-time quantitative polymerase chain reaction and flow cytometry. RESULTS: Compared with healthy controls, the PBMCs of patients with immune thrombocytopenia (ITP) had significantly increased expressions of IDO and TTS, especially IDO. However, the plasma tryptophan concentration was significantly elevated, and kynurenine concentration was significantly reduced in ITP patients. In CD4(+) and CD8(+) T cells of the ITP patients, IDO expressions were significantly lower than those in healthy controls, but in CD19(+) and CD14(+) cells, IDO expression significantly increased. Conversely, TTS expressions in CD4(+) and CD8(+) T cells of the ITP patients were significantly higher than those in healthy controls, but there was no difference either in CD19(+) or CD14(+) cells. CONCLUSION: These results suggest that the activity of IDO enzyme is insufficient in ITP patients. Increased TTS expressions from CD4(+) and CD8(+) T cells might link to a pathogenic mechanism involved in increasing survival of autoreactive T cells in ITP patients.