Low-dose decitabine modulates T cell homeostasis and restores immune tolerance in immune thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired autoimmune disease triggered by abnormal T cell immunity, especially the impairment of regulatory T (Treg) cells and helper T (Th) cell subsets. Decitabine, a hypomethylating agent promoting cell differentiation at low dose, has been demonstrated the function of increasing the number of mature polyploidy megakaryocytes in ITP as well as Treg cells in allogeneic transplantation. Recently, our clinical study proved that decitabine was effective and safe in the management of adult ITP patients, and nearly half showed sustained responses. However, whether low-dose decitabine has the potential in restoring immune tolerance in ITP is unknown. In our in vitro studies, we identified that low-dose decitabine could promote the generation and differentiation and enhance the immunosuppressive function of Treg cells. Furthermore, low-dose decitabine alleviated thrombocytopenia and regained the balance of Treg/Th cell subsets in active murine models of ITP. For patients who received low-dose decitabine therapy and showed responses, the quantity and function of Treg cells were substantially improved, whereas Th1 and Th17 cells were depressed compared with the pretreatment levels. Finally, immunophenotyping and next-generation RNA sequencing analysis showed that low-dose decitabine restored T cell homeostasis and decreased the level of proinflammatory cytokines along with the downregulation of STAT3 and Akt in refractory ITP patients. Therefore, our data reveal the immunomodulatory effect of decitabine and provide unique insights into the sustained response achieved by decitabine in the management of ITP patients. PBMCs mRNA samples of 4 responders and 3 non-responders of low-dose decitabine