What is the pathophysiology of alloimmunized refractoriness to platelet transfusions?

Updated: Sep 08, 2017
  • Author: Douglas Blackall, MD, MPH; Chief Editor: Michael A Kaliner, MD  more...
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HLA alloimmunization is the most common cause of platelet refractoriness. The immune response to non-HLA antigens, present on the platelet surface (most importantly, platelet-specific antigens or HPAs) are involved less commonly. Patients not previously sensitized may develop platelet antibodies approximately 3-4 weeks after transfusion. However, patients previously immunized by transfusion, pregnancy, or organ transplantation may develop platelet antibodies as early as 4 days after transfusion. Macrophages in the liver, spleen, and other tissues of the mononuclear phagocyte system phagocytize and destroy antibody-coated platelets.

Risk factors for developing platelet antibodies include the presence of more than 1 million donor leukocytes in transfused cellular blood products (platelets, red blood cells), transfusing ABO-mismatched platelets, the presence of an intact immune system (ie, absence of cytotoxic or immunosuppressive therapy), female sex (approximately 75% of cases), and a history of multiple transfusions (>20). [3]

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