Immunohematologic aspects of alloimmunization and alloantibody detection: A focus on pregnancy and hemolytic disease of the fetus and newborn

Alloimmunization to non-ABO, red blood cell (RBC) antigens remains one of the most clinically-relevant complexities faced by blood banking practitioners. In the setting of transfusion therapy, these antibodies raise risks for incompatibilities, while for pregnant patients they can mediate deadly forms of hemolytic disease of the fetus and newborn. As such, a thorough understanding of pathways that lead to alloimmunization, as well as the tools used by blood banks to detect alloantibodies, is critical to transfusion practice. In this review, in which alloimmunization in the setting of pregnancy will be emphasized, we will review: 1) the clinical impacts of RBC alloantibodies in the peri-partum period; 2) the current pathophysiologic mechanisms thought to influence nonABO antigen alloimmunization; 3) the strengths and weaknesses of laboratory tools used in aiding alloimmunization detection; and 4) future directions of the transfusion community related to alloimmunization impacting pregnancy.