Tumor Necrosis Factor-α Blockade Corrects Monocyte/Macrophage Imbalance in Primary Immune Thrombocytopenia

Abstract Primary immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder. Monocytes and macrophages are the major cells involved in autoantibody-mediated platelet clearance in ITP. In the present study, we found increased percentages of peripheral blood proinflammatory CD16+ monocytes and elevated frequencies of splenic tumor necrosis factor-α (TNF-α)-expressing macrophages in ITP patients compared with healthy controls. Concurrently, we observed elevated TNF-α secretion in plasma as well as higher TNF-α mRNA expression in total peripheral blood mononuclear cells and CD14+ monocytes of ITP patients. Of note, in vitro TNF-α blockade with neutralizing antibody remarkably reduced polarization to M1 macrophages by inhibiting the nuclear factor kappa B (NF-κB) signaling pathway. Moreover, TNF-α blockade dampened macrophage phagocytosis and T cell stimulatory capacity. Finally, in passive and active murine models of ITP, anti-TNF-α therapy reduced the number of nonclassical monocytes and M1 macrophages, ameliorated the retention of platelets in spleen and liver, and increased the platelet count of ITP mice. Taken together, TNF-α blockade decreased the number and function of proinflammatory subsets of monocytes and macrophages by inhibiting the NF-κB signaling pathway, leading to remarkable attenuation of antibody-mediated platelet destruction. Thus, TNF-α blockade may be a promising therapeutic strategy for the management of ITP.