Red blood cell alloimmunization immunogenetic risk factor.

Alloimmunization to blood group antigens is the result of a humoral immune response initiated by exposure to foreign antigens absent from the recipient's red blood cells (RBCs). Interestingly, not all individuals who receive mismatched RBC transfusions develop alloantibodies. Increasing evidence points to the role of the classical human leukocyte antigen (HLA) system in modulating this immune response. More recently, polymorphisms in nonclassical HLA molecules have been implicated in the regulation of inflammatory responses, particularly in patients with sickle cell disease. The role of natural fetomaternal microchimerism may also be a factor to consider in explaining individual variability in alloimmune response. The genetic diversity of both RBC antigens and HLA across ethnic groups underscores the need for high-throughput sequencing technologies to improve donor-recipient matching. In the future, genotyping strategies should aim not only to assess individual risk for alloantibody development but also to guide the selection of compatible RBC units, thereby reducing the likelihood of alloimmunization.