RESUMEN
L-glutamate, the major excitatory neurotransmitter, also has a role in non-neuronal tissues and modulates immune responses. Whether NMDA receptor (NMDAR) signalling is involved in T-cell development is unknown. In this study, we show that mouse thymocytes expressed an array of glutamate receptors, including NMDARs subunits. Sustained calcium (Ca(2+)) signals and caspase-3 activation in thymocytes were induced by interaction with antigen-pulsed dendritic cells (DCs) and were inhibited by NMDAR antagonists MK801 and memantine. NMDARs were transiently activated, triggered the sustained Ca(2+) signal and were corecruited with the PDZ-domain adaptor postsynaptic density (PSD)-95 to thymocyte-DC contact zones. Although T-cell receptor (TCR) activation was sufficient for relocalization of NMDAR and PSD-95 at the contact zone, NMDAR could be activated only in a synaptic context. In these T-DC contacts, thymocyte activation occurred in the absence of exogenous glutamate, indicating that DCs could be a physiological source of glutamate. DCs expressed glutamate, glutamate-specific vesicular glutamate transporters and were capable of fast glutamate release through a Ca(2+)-dependent mechanism. We suggest that glutamate released by DCs could elicit focal responses through NMDAR-signalling in T cells undergoing apoptosis. Thus, synapses between T and DCs could provide a functional platform for coupling TCR activation and NMDAR signalling, which might reflect on T-cell development and modulation of the immune response.
Asunto(s)
Señalización del Calcio , Calcio/metabolismo , Caspasa 3/metabolismo , Células Dendríticas/inmunología , Receptores de N-Metil-D-Aspartato/metabolismo , Glándula Tiroides/inmunología , Sistema de Transporte de Aminoácidos X-AG/metabolismo , Animales , Apoptosis , Células Dendríticas/metabolismo , Homólogo 4 de la Proteína Discs Large , Maleato de Dizocilpina/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Ácido Glutámico/metabolismo , Ácido Glutámico/farmacología , Guanilato-Quinasas , Péptidos y Proteínas de Señalización Intracelular/química , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Memantina/farmacología , Proteínas de la Membrana/química , Proteínas de la Membrana/metabolismo , Ratones , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Glándula Tiroides/citología , Glándula Tiroides/metabolismoRESUMEN
The measurement of precursor frequencies of donor anti-recipient cytotoxic T lymphocytes (CTL-p) has been shown to predict the incidence and the severity of acute graft-versus-host disease (aGVHD) in unrelated donor bone marrow transplantation (BMT). In HLA-identical sibling BMT, where aGVHD is most likely caused by minor histocompatibility antigen mismatches, this assay did not appear to be sensitive enough to provide similar predictive information. In this study, the CTL-p frequencies and the incidence and severity of aGVHD in 51 onco-hematological patients transplanted from HLA-identical siblings were compared. Sibling donors were selected on the basis of HLA identity using serological typing for HLA-A, B, C antigens, whereas HLA-DRB was tested by molecular analysis. Sibling identity was also confirmed by DNA heteroduplex analyses. Fifteen out of 21 (71%) patients with high precursor frequency (>1:100 x 10(3)) and 12 out of 30 (40%) with low precursor frequency (<1:100 x 10(3)) experienced clinically significant (II-IV) aGVHD. A significant correlation (P = 0.04) between CTL-p frequency and severe aGVHD was demonstrated. Moreover there was a positive trend for a high frequency response according to an increasing grade of aGVHD, which was statistically significant (P = 0.04). In our experience the CTL-p assay is a helpful predictive test for aGVHD in HLA-identical sibling BMT, indicating high risk patients possibly requiring additional prophylaxis.
Asunto(s)
Trasplante de Médula Ósea , Enfermedad Injerto contra Huésped/sangre , Linfocitos T Citotóxicos/inmunología , Donantes de Tejidos , Enfermedad Aguda , Adolescente , Adulto , Trasplante de Médula Ósea/inmunología , Femenino , Enfermedad Injerto contra Huésped/diagnóstico , Enfermedad Injerto contra Huésped/etiología , Neoplasias Hematológicas/complicaciones , Neoplasias Hematológicas/terapia , Prueba de Histocompatibilidad , Humanos , Recuento de Linfocitos , Masculino , Persona de Mediana Edad , Núcleo Familiar , Valor Predictivo de las Pruebas , Pronóstico , Factores de Riesgo , Sensibilidad y Especificidad , Estadísticas no Paramétricas , Quimera por Trasplante , Trasplante Homólogo/efectos adversosRESUMEN
IFN-gamma R expression is subject to contrasting modulation on human T cells. IFN-gamma R constitutive expression is low on three human malignant T cells (ST4, PF382, and Jurkat) growing in medium supplemented with serum. The addition of IFN-gamma down-modulates IFN-gamma R expression and increases both proliferation and MHC class I Ag expression. By contrast, when malignant T cells are cultured in medium without serum, IFN-gamma R expression dramatically increases and the cells undergo a slow apoptotic death. The addition of IFN-gamma enhances apoptosis and inhibits cell rescue in serum-supplemented medium. This opposite ability of IFN-gamma to stimulate malignant T cell proliferation or death correlates with the intensity of IFN-gamma R cell expression, high expression being a marker for cell apoptosis. IFN-gamma R up-modulation also occurs on malignant T cells undergoing apoptosis after treatment with dexamethasone, on irradiated normal CD3+ PBL, and on cultured normal CD3+ thymocytes. Moreover, the ability of IFN-gamma to augment apoptosis of highly IFN-gamma R-positive thymocytes suggests that its role in promoting T cell apoptosis is also important in physiologic conditions.