RESUMEN
T cells form immunological synapses with professional antigen-presenting cells (APCs) resulting in T cell activation and the acquisition of peptide antigen-MHC (pMHC) complexes from the plasma membrane of the APC. They thus become APCs themselves. We investigate the functional outcome of T-T cell antigen presentation by CD4 T cells and find that the antigen-presenting T cells (Tpres) predominantly differentiate into regulatory T cells (Treg), whereas T cells that have been stimulated by Tpres cells predominantly differentiate into Th17 pro-inflammatory cells. Using mice deficient in pMHC uptake by T cells, we show that T-T antigen presentation is important for the development of experimental autoimmune encephalitis and Th17 cell differentiation in vivo. By varying the professional APC:T cell ratio, we can modulate Treg versus Th17 differentiation in vitro and in vivo, suggesting that T-T antigen presentation underlies proinflammatory responses in conditions of antigen scarcity.
Asunto(s)
Presentación de Antígeno/inmunología , Antígenos/metabolismo , Polaridad Celular/inmunología , Células Th17/inmunología , Animales , Antígenos CD28/metabolismo , Diferenciación Celular/inmunología , Membrana Celular/metabolismo , Células Dendríticas/inmunología , Modelos Animales de Enfermedad , Encefalomielitis Autoinmune Experimental/inmunología , Encefalomielitis Autoinmune Experimental/patología , Regulación de la Expresión Génica , Genoma , Antígenos de Histocompatibilidad Clase II/inmunología , Ratones Endogámicos C57BL , Linfocitos T Reguladores/inmunología , Transcripción Genética , Trogocitosis , Proteínas de Unión al GTP rho/deficiencia , Proteínas de Unión al GTP rho/metabolismoRESUMEN
Signal strength controls the outcome of αß T cell selection in the thymus, resulting in death if the affinity of the rearranged TCR is below the threshold for positive selection, or if the affinity of the TCR is above the threshold for negative selection. Here we show that deletion of the GTPase RRAS2 results in exacerbated negative selection and above-normal expression of positive selection markers. Furthermore, Rras2-/- mice are resistant to autoimmunity both in a model of inflammatory bowel disease (IBD) and in a model of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE). We show that MOG-specific T cells in Rras2-/- mice have reduced affinity for MOG/I-Ab tetramers, suggesting that enhanced negative selection leads to selection of TCRs with lower affinity for the self-MOG peptide. An analysis of the TCR repertoire shows alterations that mostly affect the TCRα variable (TRAV) locus with specific VJ combinations and CDR3α sequences that are absent in Rras2-/- mice, suggesting their involvement in autoimmunity.