Antiplatelet antibody predicts platelet desialylation and apoptosis in immune thrombocytopenia

Haematologica. 2022 Sep 1;107(9):2195-2205. doi: 10.3324/haematol.2021.279751.

Abstract

Immune thrombocytopenia (ITP) is a bleeding disorder caused by dysregulated B- and T- cell functions, which lead to platelet destruction. A well-recognized mechanism of ITP pathogenesis involves anti-platelet and anti-megakaryocyte antibodies recognizing membrane glycoprotein (GP) complexes, mainly GPIb/IX and GPIIb/IIIa. In addition to the current view of phagocytosis of the opsonised platelets by splenic and hepatic macrophages via their Fc γ receptors, antibodyinduced platelet desialylation and apoptosis have also been reported to contribute to ITP pathogenesis. Nevertheless, the relationship between the specific thrombocytopenic mechanisms and various types of anti-platelet antibodies has not been established. In order to ascertain such association, we used sera from 61 ITP patients and assessed the capacity of anti-platelet antibodies to induce neuraminidase 1 (NEU1) surface expression, RCA-1 lectin binding and loss of mitochondrial inner membrane potential on donors' platelets. Sera from ITP patients with detectable antibodies caused significant platelet desialylation and apoptosis. Anti-GPIIb/IIIa antibodies appeared more capable of causing NEU1 surface translocation while anti-GPIb/IX complex antibodies resulted in a higher degree of platelet apoptosis. In ITP patients with anti-GPIIb/IIIa antibodies, both desialylation and apoptosis were dependent on FcγRIIa signaling rather than platelet activation. Finally, we confirmed in a murine model of ITP that destruction of human platelets induced by anti-GPIIb/IIIa antibodies can be prevented with the NEU1 inhibitor oseltamivir. A collaborative clinical trial is warranted to investigate the utility of oseltamivir in the treatment of ITP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies
  • Apoptosis
  • Autoantibodies
  • Blood Platelets
  • Humans
  • Mice
  • Oseltamivir
  • Platelet Glycoprotein GPIIb-IIIa Complex
  • Platelet Glycoprotein GPIb-IX Complex
  • Purpura, Thrombocytopenic, Idiopathic*
  • Thrombocytopenia* / etiology

Substances

  • Antibodies
  • Autoantibodies
  • Platelet Glycoprotein GPIIb-IIIa Complex
  • Platelet Glycoprotein GPIb-IX Complex
  • Oseltamivir

Grants and funding

Funding: This work was supported by the National Health and Medical Research Council project grant to BHC (GNT 1012409) as well as St. George and Sutherland Medical Research Foundation Grant to JSP. SSZ received NSW Ministry of Health PhD Scholarship. In Vivo data presented in this work was acquired at the Mark Wainright Analytical Centre (MWAC) of UNSW Sydney, which is in part funded by the Research Infrastructure Program of UNSW.