RESUMO
Recent data have demonstrated that treatment with alphabeta-TCR(+)CD3(+)CD4(-)CD8(-)NK1.1(-) double negative (DN) regulatory T cells (Tregs) inhibits autoimmune diabetes and enhances allotransplant and xenotransplant survival in an Ag-specific fashion. However, the mechanisms whereby DN Tregs suppress Ag-specific immune responses remain largely unknown. In this study, we demonstrate that murine DN Tregs acquire alloantigen in vivo via trogocytosis and express it on their cell surface. Trogocytosis requires specific interaction of MHC-peptide on APCs and Ag-specific TCR on DN Tregs, as blocking this interaction prevents DN Treg-mediated trogocytosis. Acquisition of alloantigen by DN Tregs was required for their ability to kill syngeneic CD8(+) T cells. Importantly, DN Tregs that had acquired alloantigen were cytotoxic toward Ag-specific, but not Ag-nonspecific, syngeneic CD8(+) T cells. These data provide new insight into how Tregs mediate Ag-specific T cell suppression and may enhance our ability to use DN Tregs as a therapy for transplant rejection and autoimmune diseases.
Assuntos
Epitopos/imunologia , Tolerância Imunológica , Linfócitos T Reguladores/citologia , Linfócitos T Reguladores/imunologia , Animais , Antígenos Ly , Antígenos de Superfície/genética , Antígenos CD4/genética , Antígenos CD8/genética , Células Cultivadas , Testes Imunológicos de Citotoxicidade , Isoantígenos/imunologia , Isoantígenos/metabolismo , Lectinas Tipo C/genética , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Camundongos SCID , Camundongos Transgênicos , Subfamília B de Receptores Semelhantes a Lectina de Células NK , Fragmentos de Peptídeos/imunologia , Fragmentos de Peptídeos/metabolismo , Linfócitos T Citotóxicos/imunologia , Linfócitos T Citotóxicos/metabolismo , Linfócitos T Reguladores/metabolismoRESUMO
Recent studies have indicated that regulatory T cell (Treg)-mediated suppression may depend on interactions with antigen presenting cells (APCs). TCRαß(+)CD3(+)CD4(-)CD8(-)NK1.1(-) double-negative (DN) Tregs have been shown to be able to suppress effector T cells in vitro in mice and humans, and control various diseases in an antigen (Ag)-specific manner in murine models. Studies on DN Tregs have been focused on their suppressive effect on T cells. However, the nature of APCs that can effectively activate DN Tregs as well as the effect of DN Tregs on APCs, have not previously been studied. In this report, we investigated the interactions of DN Tregs with APCs. We found that although stimulation with naïve allogeneic APCs could activate DN Tregs, it failed to induce proliferation of DN Tregs. Interestingly, stimulation with LPS-activated allogeneic APCs significantly augmented the proliferation of DN Tregs compared to naïve allogeneic APCs. Importantly, the expanded DN Tregs can maintain their suppressive function. Further, DN Tregs proliferated in the presence of LPS-activated B cells in an Ag-specific fashion. Although DN Tregs were not able to down regulate the expression of CD80 or CD86 on LPS-activated B cells, they could kill activated allogeneic as well as syngeneic B cells via a perforin-dependent pathway, indicating that eliminating activated B cells may contribute to DN Treg-mediated suppression. These data provide important insights into the interactions of DN Tregs with APCs and may facilitate production of functional Ag-specific DN Tregs in a clinical setting.