Complement system

Red Cell

Biology

Rh blood group system

Fetus

Red blood cell

Immunology

Autoantibody

Hemolytic disease of the newborn (ABO)

Genetics

Hemolytic anemia

Isoantibodies

Internal medicine

Hemolysis

Blood transfusion

Medicine

Disease

Antibody

Pregnancy

Transfusion Clinique et Biologique

Red blood cell (RBC) alloimmunization is more common in patients with sickle cell disease (SCD) than in any other studied patient population. The high prevalence of RBC alloimmunization is multi-factorial, likely involving the chronic hemolysis and inflammatory status of SCD itself, the transfusion burden of patients, and the RH genetic diversity of patients and blood donors, among other reasons. Antibody evanescence, or the decrease of RBC alloantibodies below levels detectable by blood bank testing, occurs frequently with fewer than 30% of alloantibodies estimated to be detected by current screening practices. Evanescence increases the likelihood that a patient with SCD will have a delayed hemolytic transfusion reaction upon future RBC exposure, with previously undetected alloantibodies coming roaring back in an anamnestic manner after exposure to the cognate RBC antigen. A subset of patients having delayed hemolytic transfusion reactions go on to experience hyperhemolysis; some but not all cases of hyperhemolysis are associated with previously evanescent RBC alloantibodies. There is an increasing appreciation of the association between RBC alloantibodies and RBC autoantibodies, as well as involvement of the alternative complement pathway in some instances of hyperhemolysis. A case report in this manuscript describes a highly alloimmunized patient with SCD who experiences a delayed hemolytic transfusion reaction with bystander hemolysis due to a previously evanescent, complement binding anti-M RBC alloantibody. Additional studies, including those involving multiple centers and countries, are needed to further understand RBC alloimmunization in patients with SCD and to develop strategies to prevent or mitigate potentially life-threatening hemolytic transfusion reactions. L'alloimmunisation anti-érythrocytaire post-transfusionnelle est plus fréquente au cours de la drépanocytose que dans d'autres pathologies. Cette prévalence élevée est d'origine multifactorielle avec notamment l'hémolyse chronique, le statut inflammatoire, le régime transfusionnel, le polymorphisme des groupes sanguins, et entre autres les variants RH. L'évanescence des anticorps, dans plus de 30 % des cas, représente une cause importante d'hémolyse post-transfusionnelle retardée (HPTR), par restimulation de ces anticorps non connus dans l'historique et indétectable avant la transfusion. De plus, il existe une fréquence non négligeable d'autoanticorps associés à des alloanticorps au cours de ces réactions transfusionnelles. Enfin, sur le plan des mécanismes la place de l'activation via la voie alterne du complément au cours de ces réactions semble jouer un rôle important. Dans ce manuscrit, nous décrivons un cas d'HPTR, avec hyperhémolyse, via un anti-M fixant le complément, et auyat présenté une évanescence. Des études à l'échelon international sont nécessaires pour comprendre les mécanismes d'alloimmunisation et l'implication des anticorps dans les HPTR.

Red blood cell alloimmunization and delayed hemolytic transfusion reactions in patients with sickle cell disease