Decreased Expression of IL‐35 and Its Receptor Contributes to Impaired Megakaryopoiesis in the Pathogenesis of Immune Thrombocytopenia

Abstract Recent findings have shown that the level of interleukin‐35 (IL‐35) is abnormal in several autoimmune diseases. Nonetheless, whether IL‐35 participates in the pathogenesis of immune thrombocytopenia (ITP) remains unclear. The current study investigates whether IL‐35 modulates megakaryopoiesis. The results show that IL‐35 receptors are progressively expressed on bone marrow megakaryocytes during the in vitro differentiation of CD34+ progenitors. IL‐35 increases the number of megakaryocyte colony‐forming units through the Akt pathway. The level of bone marrow IL‐35 is reduced in ITP patients, and the decreased level of IL‐35 may inhibit megakaryopoiesis. Then, the potential causes of decreased IL‐35 in ITP patients are explored. The primary type of cell that secretes IL‐35, known as IL‐35‐producing regulatory T cells (iTr35), is reduced in ITP patients. Bone marrow mesenchymal stem cells (MSCs) from ITP patients exhibit an impaired capability of inducing iTr35 due to enhanced apoptosis, which may contribute to the reduced level of bone marrow IL‐35 in ITP patients. Iguratimod promotes megakaryocyte development and differentiation by elevating the expression of IL‐35 receptors on megakaryocytes. Iguratimod improves response rates and reduces bleeding symptoms in corticosteroid‐resistant ITP patients.