T-cell immune responses to Wilms tumor 1 protein in myelodysplasia responsive to immunosuppressive therapy

Abstract

Clinical observations and laboratory evidence link bone marrow failure in myelodysplastic syndrome (MDS) to a T cell–mediated immune process that is responsive to immunosuppressive treatment (IST) in some patients. Previously, we showed that trisomy 8 MDS patients had clonally expanded CD8+ T-cell populations that recognized aneuploid hematopoietic progenitor cells (HPC). Furthermore, microarray analyses showed that Wilms tumor 1 (WT1) gene was overexpressed by trisomy 8 hematopoietic progenitor (CD34+) cells compared with CD34+ cells from healthy donors. Here, we show that WT1 mRNA expression is up-regulated in the bone marrow mononuclear cells of MDS patients with trisomy 8 relative to healthy controls and non–trisomy 8 MDS; WT1 protein levels were also significantly elevated. In addition, using a combination of physical and functional assays to detect the presence and reactivity of specific T cells, respectively, we demonstrate that IST-responsive MDS patients exhibit significant CD4+ and CD8+ T-cell responses directed against WT1. Finally, WT1-specific CD8+ T cells were present within expanded T-cell receptor Vβ subfamilies and inhibited hematopoiesis when added to autologous patient bone marrow cells in culture. Thus, our results suggest that WT1 is one of the antigens that triggers T cell–mediated myelosuppression in MDS.