Cellular and Molecular Analysis of Notch Signaling in T Cells after Allogeneic Bone Marrow Transplantation

[摘要] Allogeneic bone marrow transplantation (allo-BMT) is a potentially curative therapy for patients with cancer and hematological disorders.However, its success is limited by graft-versus-host disease (GVHD). Less than 50% of patients who manifest with acute GVHD symptoms respond to corticosteroids, underscoring the need to develop better therapeutics.Notch signaling has emerged as a critical regulator of T cell alloimmunity after allo-BMT.During allo-BMT, Notch signals are mediated by Notch1/2 receptors and Delta-like1/4 ligands.Systemic inhibition of Delta-like1/4 ligands with neutralizing antibodies results in long-term protection from acute GVHD.In this thesis, I first investigated the spatial and temporal regulation of Notch signals during allo-BMT.A single dose of Dll1/4 neutralizing antibodies at the time of allo-BMT was sufficient to confer long-term protection from GVHD mortality.In contrast, delayed administration of antibodies by only two days failed to protect from GVHD.To determine the cellular source(s) that delivered Notch signals to alloreactive T cells during this window of activity, I genetically inactivated Dll1 and Dll4 Notch ligands within donor hematopoietic, host hematopoietic, and host nonhematopoietic tissues.Mice that lacked Dll1 and Dll4 expression selectively within Ccl19+ fibroblastic cells were profoundly protected from GVHD lethality.Thus, these data revealed that Ccl19+ fibroblasts deliver early Notch signals to alloantigen-specific T cells.Next, I developed a novel model of acute GVHD with alloantigen-specific CD4+ donor T cells to study molecular events during the critical 48-hour period of Notch activity.Notch inhibition in alloantigen-specific T cells preserved early activation marker expression, IL-2 production, and initial proliferation.In contrast, Notch inhibition impaired proinflammatory cytokine production and reduced both mTORC1 and Ras/MAPK activity.Transcriptional profiling revealed that Notch inhibition diminished expression of cytokines, cytokine receptors, and Myc target genes.Collectively, my data demonstrated that fibroblastic niches deliver critical Notch signals that are essential for acquisition of T effector functions but not for initial proliferation.Work in this thesis introduces the novel concept that early interactions between donor alloreactive T cells and host fibroblastic niches dictate the long-term outcome of GVHD.A deeper understanding of these interactions could lead to exciting new therapies for alloimmune and autoimmune disorders.

[发布机构] University of Michigan

[效力级别] Molecular

[关键词] Notch signaling after allogeneic bone marrow transplantation;Molecular;Cellular and Developmental Biology;Science;Cellular & Molec Biology PhD