Younger blood from older donors: Admitting ignorance and seeking stronger data and clinical trials?

An overview of red blood cell and platelet alloimmunisation in transfusion

Post-transfusion alloimmunisation is the main complication of all those observed after one or more transfusion episodes. Alloimmunisation is observed after the transfusion of red blood cell concentrates but also of platelet concentrates. Besides alloimmunisation due to antigens carried almost exclusively by red blood cells such as those of the Rhesus-Kell system, alloimmunisation often raises against HLA antigens; the main responsibility for that, apart from platelet transfusions, lies with residual leukocytes in the products transfused, hence the central importance of effective leukoreduction right from the blood product preparation stage. Alloimmunization is not restricted to transfusion, but it is also observed during pregnancies, carrying out microtransfusions of blood from the fetus immunizing the mother through the placenta (in a retrograde way). Preexisting maternal-fetal immunization can complicate a transfusion program and intensify the creation of alloantibodies in several blood and tissue group systems. The occurrence of autoantibodies, created by several pathogenic reasons, can also interfere with the propensity of certain recipients of blood components to produce alloantibodies. The genetic condition of individuals is in fact strongly linked to the ability or not to recognize antigenic variants foreign to their own biological program and mount an alloimmune response. Some hemoglobin diseases, in carriers of which transfusions can be iterative and lifelong, are complicated by frequent alloimmunizations and amplification of the complications of these alloimmunizations, imposing even stricter transfusion rules. This review details the mechanisms favoring the occurrence of alloimmunization and the immunological principles for the production of molecular and cellular tools for alloimmunization. It concludes with the main preventive measures available to limit the occurrence of these frequent complications of varying severity but sometimes severe.

Transfused trauma patients have better outcomes when transfused with blood components from young donors

The physiology of tissue healing and aging share common pathways. Both patient age and tissue healing are crucial factors predicting outcomes in trauma patients. The presented hypothesis focuses on the concept that transfused trauma patients have better outcomes when transfused with blood components from young donors. The age of the donor of a blood transfusion could affect recovery following a major traumatic insult and help avoid postinjury immune paralysis and its associated complications. The frequent transfusion of blood components to the severely injured trauma patient provides an opportunity for the recipient to benefit from the potentially favourable effect of blood originating from young donors. Different types of evidence support the presented hypothesis including work on soluble circulating factors, research on animal parabiontic models and epidemiological studies. Theories on the role of transfusion of cells, on bone marrow and on senolytics also represent grounds to elaborate pathways to test this hypothesis. The precise molecular mechanism underlying this hypothesis is uncertain. A beneficial effect on trauma patients following transfusion of blood could be due to a positive effect of blood donated from younger donors or instead to the lack of a negative effect possibly occurring when transfusing blood from older donors. Either way, identifying this mechanism would provide a powerful tool enhance long and short term recovery after trauma.