Leukoreduction of blood transfusions does not diminish transfusion-associated microchimerism in trauma patients

BACKGROUND: Transfusion of trauma patients can result in long-term survival of donor white blood cells (WBCs) or “transfusion-associated microchimerism” (TA-MC). The aim was to determine whether leukoreduction of blood transfusions, advocated to reduce the immunomodulatory effect of transfusion, decreases the likelihood of developing TA-MC. STUDY DESIGN AND METHODS: A subgroup of trauma patients from a randomized trial was examined, evaluating the risk of infection following leukoreduced versus nonleukoreduced blood transfusion. Patients’ blood was sampled at least 1 month after hospital discharge, and TA-MC was assessed with quantitative allele-specific polymerase chain reaction detection of differences at the HLA-DR locus or a panel of insertion-deletion polymorphism loci distributed throughout the chromosomal complement. At the time of blood sampling, a scripted interview was used to ascertain symptoms suggestive of chronic graft-versus host disease (cGVHD). RESULTS: For 67 patients evaluated, the mean age was 43 ± 17 years and mean Injury Severity Score was 24 ± 12. Median time from injury to blood sampling for TA-MC was 240 (interquartile range, 116-360) days. Nine of 32 patients (28%) in the nonleukoreduced transfusion group developed TA-MC compared to 13 of 35 patients (37%) in the leukoreduced group (p = 0.43). Subjects with TA-MC were no more likely than subjects without TA-MC to have at least one symptom suggestive of cGVHD (64% vs. 76%, respectively). CONCLUSIONS: TA-MC seems to be a prevalent condition among injured patients at the second of two regional trauma centers evaluated, suggesting that it is a common phenomenon after transfusion in the setting of injury. Although leukoreduction removes greater than 99.9 percent of donor WBCs, it fails to prevent or even substantially reduce the likelihood of developing TA-MC. TA-MC does not appear to be strongly associated with symptoms suggestive of cGVHD several months after transfusion.