RESUMO
Lymphocyte activation gene-3 (LAG-3) is an inhibitory receptor expressed by CD4+ T cells and tempers their homeostatic expansion. Because CD4+ T cell proliferation is tightly coupled to bioenergetics, we investigate the role of LAG-3 in modulating naive CD4+ T cell metabolism. LAG-3 deficiency enhances the metabolic profile of naive CD4+ T cells by elevating levels of mitochondrial biogenesis. In vivo, LAG-3 blockade partially restores expansion and the metabolic phenotype of wild-type CD4+ T cells to levels of Lag3-/- CD4+ T cells, solidifying that LAG-3 controls these processes. Lag3-/- CD4+ T cells also demonstrate greater signal transducer and activator of transcription 5 (STAT5) activation, enabling resistance to interleukin-7 (IL-7) deprivation. These results implicate this pathway as a target of LAG-3-mediated inhibition. Additionally, enhancement of STAT5 activation, as a result of LAG-3 deficiency, contributes to greater activation potential in these cells. These results identify an additional mode of regulation elicited by LAG-3 in controlling CD4+ T cell responses.
Assuntos
Antígenos CD/fisiologia , Linfócitos T CD4-Positivos , Metabolismo Energético/genética , Mitocôndrias/fisiologia , Biogênese de Organelas , Animais , Antígenos CD/genética , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD4-Positivos/ultraestrutura , Células Cultivadas , Feminino , Ativação Linfocitária/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/genética , Mitocôndrias/metabolismo , Fase de Repouso do Ciclo Celular/genética , Proteína do Gene 3 de Ativação de LinfócitosRESUMO
In spite of tolerance mechanisms, some individuals develop T-cell-mediated autoimmunity. Posttranslational modifications that increase the affinity of epitope presentation and/or recognition represent one means through which self-tolerance mechanisms can be circumvented. We investigated T-cell recognition of peptides that correspond to modified ß-cell antigens in subjects with type 1 diabetes. Modified peptides elicited enhanced proliferation by autoreactive T-cell clones. Endoplasmic reticulum (ER) stress in insulinoma cells increased cytosolic calcium and the activity of tissue transglutaminase 2 (tTG2). Furthermore, stressed human islets and insulinomas elicited effector responses from T cells specific for modified peptides, suggesting that ER stress-derived tTG2 activity generated deamidated neoepitopes that autoreactive T cells recognized. Patients with type 1 diabetes had large numbers of T cells specific for these epitopes in their peripheral blood. T cells with these specificities were also isolated from the pancreatic draining lymph nodes of cadaveric donors with established diabetes. Together, these results suggest that self-antigens are enzymatically modified in ß-cells during ER stress, giving rise to modified epitopes that could serve to initiate autoimmunity or to further broaden the antigenic repertoire, activating potentially pathogenic CD4+ T cells that may not be effectively eliminated by negative selection.
