Transfusion immunomodulation or TRIM: what does it mean clinically?

Evidence from a variety of sources indicate that allogeneic blood transfusions can induce clinically significant immunosuppression, as well as other effects, in recipients. This clinical syndrome is generally referred to in the Transfusion Medicine literature as transfusion-associated immunomodulation, or TRIM. TRIM has been linked to an improved clinical outcome in the setting of renal allograft transplantation. Possible deleterious TRIM-associated effects include an increased rate of cancer recurrence and of post-operative bacterial infection. The recognition that TRIM can increase morbidity and mortality in allogeneically transfused individuals has become a major concern for those involved in Transfusion Medicine. However, based on available randomized controlled trials, whether TRIM predisposes recipients to increased risk for cancer recurrence and/or bacterial infection is still unproven. In contrast, data from experimental animal studies suggest that TRIM is an immunologically mediated biological effect, associated with the transfusion of allogeneic leukocytes; an effect, which can be completely ameliorated by the pre-storage leukoreduction of blood products. Relevantly, several (n = 5) recent large observational trials have provided important evidence for the existence of deleterious TRIM and related effects (mortality and organ dysfunction) of leukocyte-containing allogeneic cellular blood products. These latter data suggest that allogeneic blood product transfusions, containing leukocytes, are associated with an increased risk both for mortality, and organ dysfunction in recipients.