Alloimmunization is an undesirable iatrogenic effect of transfusion and transplantation. In fact, recipients can be considered as responders or not responders, in a continuum from tolerance, including organ transplantation and transfusion, to polyimmunized and refractory patients. New models and large studies have enabled a better understanding of the mechanisms that induce specific alloantibody (alloAb) generation. Here, we focus on risk factors of alloimmunization. We review the alloantibody characteristics, summarize the different leukocytes involved in their induction, and suggest some hypotheses.
