What are the consequences of alloimmunization to blood-based antigens?

Updated: Sep 08, 2017
  • Author: Douglas Blackall, MD, MPH; Chief Editor: Michael A Kaliner, MD  more...
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The consequences of alloimmunization to blood-based antigens include the following clinical manifestations:

  • Alloimmunization against RBCs

    • Acute intravascular hemolytic transfusion reactions (rarely a consequence of alloimmunization and almost always caused by ABO antibodies) [1]

    • Delayed hemolytic transfusion reactions (DHTRs) (hemolysis caused by RBC alloantibodies typically presenting clinically 7–14 days after transfusion)

    • Hemolytic disease of the fetus and newborn (mother's alloimmunization against red blood cell fetal antigens, most often resulting from previous pregnancies)

  • Alloimmunization against platelets (platelet-specific or HLA class I antigens)

    • Refractoriness to platelet transfusion (an increase in the platelet count after platelet transfusion that is significantly lower than expected [eg, < 30% of predicted 10-60 min posttransfusion or < 20% at 18-24 h posttransfusion])

    • Posttransfusion purpura (thrombocytopenia after transfusion of red cells or other platelet-containing products, associated with the presence of platelet alloantibodies)

    • Neonatal alloimmune thrombocytopenia (mother's alloimmunization against fetal  platelet antigens, most often resulting from previous pregnancies but can be seen in a first pregnancy)

  • Alloimmunization against granulocytes (granulocyte-specific or HLA antigens)

  • Refractoriness to granulocyte transfusion

    • Febrile nonhemolytic transfusion reactions

    • Transfusion-related acute lung injury (ie, a transfusion reaction in which donor HLA antibodies react with recipient white blood cell antigens)

  • Transplant rejection

    • Alloimmunization against HLA antigens

    • Alloimmunization against blood cell antigens in bone marrow transplantation leading to hemolysis and the possibility of delayed engraftment

Hemolytic transfusion reactions, posttransfusion purpura, febrile nonhemolytic transfusion reactions, and transfusion-related acute lung injury are discussed in Transfusion Reactions. Hemolytic disease in newborns and neonatal alloimmune thrombocytopenia are discussed in other sections of Medscape Reference. Transplant rejection is discussed in Assessment and Management of the Renal Transplant Patient.

DHTRs and refractoriness to platelet transfusions are discussed in this article. Refractoriness to granulocyte transfusion involves either HLA or granulocyte-specific antibodies and is similar to platelet refractoriness, except that refractoriness to granulocyte transfusion results in the patient failing to respond clinically to the infused granulocytes. Because granulocyte transfusions are rarely used, they are not discussed further in this article.

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