Clinical Effects and Possible Mechanisms of Transfusion-Related Immunomodulation

Allogeneic blood components are commonly transfused in trauma, surgery, and intensive care units and are related with adverse effects, such as postoperative infections, multi-organ failure, and mortality. The adverse effects of blood transfusions on the immune system are called as transfusion-related immunomodulation (TRIM). Many clinical trials are conducted to show the clinical effects of TRIM. They found in different clinical settings controversial results. There are many possible mechanisms of TRIM. Although until now, the exact mechanisms are not elucidated resulting in a challenge to unravel this complex interaction between immunomodulation and clinical events leading to morbidity and mortality. It has been postulated that allogeneic leukocytes are associated with the clinical adverse effects of TRIM that predominantly is observed in high-risk patients as cardiovascular surgery. Allogeneic leukocytes could activate inflammation cascade leading to adverse events in high-risk patients. Also other blood components as red cells, plasma, and platelets can play a role in the development of inflammatory complications after blood transfusions. In this review, we will discuss the clinical effects and the possible mechanisms of TRIM in relation with allogeneic leukocytes and mediators derived from allogeneic blood transfusions