T Cell Mediated Autologous Cytotoxicity Against Hematopoietic Precursor Cells in Low and Intermediate-1 Risk Myelodysplastic Syndrome.

The immune system plays a role in the pathogenesis of myelodysplastic syndrome (MDS) but its precise contribution to disease development and control is not fully clarified. T cell activation could reflect undesired autoimmune reactions against normal hematopoietic precursor cells as well as effective immune-surveillance against dysplastic clones. We have investigated lymphocyte subsets and activation markers of 42 low risk and intermediate-1 risk MDS patients and compared them to those of intermediate-2 risk, high risk MDS patients, and healthy donors. In low and intermediate-1 risk MDS patients, we have found an activated state of lymphocytes, determined by increased percentages of effector T cells with cytotoxic profile, increased number of clonal expansions, increased frequencies of Wilms’ Tumor 1 (WT1) specific lymphocytes and decreased regulatory T cell activation, as compared to healthy donors. Moreover, we demonstrate autologous T cell mediated cytotoxicity against aberrant hematopoietic precursor cells. These findings provide evidence for the existence of immune-surveillance in the pathogenesis of low and intermediate-1 risk MDS patients. Our data are important for adequate evaluation of the role of immune-modulatory drugs in the future and justify the reconsideration of the role of immune-suppressing therapy for low and intermediate-1 risk MDS patients.