Platelets in ITP: Victims in Charge of Their Own Fate?
Vivianne S. Nelson,
Anne-Tess C. Jolink,
Sufia N. Amini,
Jaap Jan Zwaginga,
Tanja Netelenbos,
John W. Semple,
Leendert Porcelijn,
Masja de Haas,
Martin R. Schipperus,
Rick Kapur
Affiliations
Vivianne S. Nelson
Department of Hematology, Haga Teaching Hospital, 2545 AA The Hague, The Netherlands
Anne-Tess C. Jolink
Sanquin Research, Department of Experimental Immunohematology, Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, The Netherlands
Sufia N. Amini
Department of Hematology, Haga Teaching Hospital, 2545 AA The Hague, The Netherlands
Jaap Jan Zwaginga
Department of Hematology, Leiden University Medical Center (LUMC), 2333 ZA Leiden, The Netherlands
Tanja Netelenbos
Department of Hematology, Haga Teaching Hospital, 2545 AA The Hague, The Netherlands
John W. Semple
Division of Hematology and Transfusion Medicine, Lund University, 221 84 Lund, Sweden
Leendert Porcelijn
Sanquin Diagnostic Services, Department of Immunohematology Diagnostics, 1066 CX Amsterdam, The Netherlands
Masja de Haas
Sanquin Research, Department of Experimental Immunohematology, Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, The Netherlands
Martin R. Schipperus
Department of Hematology, University Medical Center Groningen (UMCG), 9713 GZ Groningen, The Netherlands
Rick Kapur
Sanquin Research, Department of Experimental Immunohematology, Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, The Netherlands
Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder. The pathophysiological mechanisms leading to low platelet levels in ITP have not been resolved, but at least involve autoantibody-dependent and/or cytotoxic T cell mediated platelet clearance and impaired megakaryopoiesis. In addition, T cell imbalances involving T regulatory cells (Tregs) also appear to play an important role. Intriguingly, over the past years it has become evident that platelets not only mediate hemostasis, but are able to modulate inflammatory and immunological processes upon activation. Platelets, therefore, might play an immuno-modulatory role in the pathogenesis and pathophysiology of ITP. In this respect, we propose several possible pathways in which platelets themselves may participate in the immune response in ITP. First, we will elaborate on how platelets might directly promote inflammation or stimulate immune responses in ITP. Second, we will discuss two ways in which platelet microparticles (PMPs) might contribute to the disrupted immune balance and impaired thrombopoiesis by megakaryocytes in ITP. Importantly, from these insights, new starting points for further research and for the design of potential future therapies for ITP can be envisioned.
