Table 2.

Recipient variables that may impact RBC alloimmunization

Genetic Factors – MHC/HLA type and the ability to present the RBC antigen – Degree to which the recipient views the RBC antigen as foreign – Polymorphisms of immunoregulatory elements (CD81, TRIM 21) – Inherited disease states (autoimmunity, sickle cell disease)

Immune status – Inherited or acquired immune activation – Status and phenotype/function of regulatory immune cell subsets – Reticuloendothelial cell considerations, including location of RBC consumption and phenotype/function of antigen-presenting cells

Prior antigen exposures – Including RBC exposures or exposures to non-RBC antigens with overlapping peptide sequences to RBC antigens – Avenue of exposures, including: – Transfusion – Pregnancy – Environmental exposures – Mucosal exposures (e.g. for tolerance induction)