Volume 46, November 2006 TRANSFUSION 1863 Blackwell Publishing IncMalden, USATRFTransfusion0041-11322006 American Association of Blood BanksNovember 2006461118631869Original Article LEUKOREDUCTION AND MICROCHIMERISMUTTER ET AL. ABBREVIATIONS: BSRI = Blood Systems Research Institute; cGVHD = chronic graft-versus-host disease; HMC = Harborview Medical Center; IQR = interquartile range; QAS-PCR = quantitative allele-specific polymerase chain reaction; TA-MC = transfusion-associated microchimerism. From the Department of Surgery, Harborview Medical Center/ University of Washington, Seattle, Washington; the Department of Surgery, University of California, Davis, Medical Center, Sacramento, California; the Blood Systems Research Institute, San Francisco, California; the Department of Laboratory Medicine, University of California, San Francisco; and the Puget Sound Blood Center, Seattle, Washington. Address correspondence to: Garth H. Utter, MD, MSc, Department of Surgery, University of California, Davis, Medical Center, 2315 Stockton Boulevard, Room 4206, Sacramento, CA 95817; e-mail: garth.utter@ucdmc.ucdavis.edu. This project was supported by Grants P50-HL-54476 and P50-HL073996-01 from the National Heart, Lung, and Blood Institute and Grant R01 G66117-01 from the National Institute of General Medical Sciences. This study was also funded in part by a grant from the Blood Systems Foundation, Scottsdale, AZ. Received for publication January 27, 2006; revision received April 24, 2006, and accepted May 1, 2006. doi: 10.1111/j.1537-2995.2006.00991.x TRANSFUSION 2006;46:1863-1869. TRANSFUSION COMPLICATIONS Leukoreduction of blood transfusions does not diminish transfusion-associated microchimerism in trauma patients Garth H. Utter, Avery B. Nathens, Tzong-Hae Lee, William F. Reed, John T. Owings, Theresa A. Nester, and Michael P. Busch 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. ersistence of allogeneic donor white blood cells (WBCs) after transfusion, or transfusion-associ- ated microchimerism (TA-MC), appears to occur relatively frequently in trauma patients. We have observed TA-MC to persist for at least 3 years, the longest follow-up to date, 1,2 and to involve multiple immunophe- notypic lineages of WBCs suggestive of broad hematopoi- etic engraftment. 1 TA-MC was not associated with obvious acute adverse effects in one small cohort we evaluated, 3 but other investigators have suggested that microchimer- ism in other settings may be associated with the develop- ment of chronic autoimmune disorders. 4-9 Leukoreduction of blood transfusions, which typi- cally reduces the concentration of donor WBCs from P