title: High-level long-term white blood cell microchimerism after transfusion of leukoreduced blood components to patients resuscitated after severe traumatic injury.
abstract: BACKGROUND
  Long-term white blood cell (WBC) microchimerism (MC), of at least 2 years, has been reported in trauma patients receiving fresh nonleukoreduced (non-LR) blood. It is unknown, however, whether this occurs with LR blood products that are nearly devoid of WBCs. Twenty-seven patients transfused with LR and non-LR blood products were studied after severe traumatic injury. A secondary aim was to explore donor-recipient mixed lymphocyte reactivity in vitro.
  
  
  METHODS
  To quantify MC, allele-specific real-time polymerase chain reaction assays were developed targeting HLA Class II sequence polymorphisms. Extensive validation showed that these assays reliably detect a single copy of target sequence in a complex allogeneic background without false positivity.
  
  
  RESULTS
  At a median follow-up of 26 months (range, 24-39 months), long-term MC was observed in 3 of 20 patients (15%) who received non-LR blood products and 2 of 7 (29%) who received LR blood products. The maximum MC ranged from 0.40 to 4.90 percent of circulating WBCs and appeared, by Class II genotype analysis, to be attributable to a single donor.
  
  
  CONCLUSIONS
  It is concluded that robust levels of long-term MC, apparently traceable to a single donor, occur at similar frequency despite leukoreduction of transfused blood products. Exploratory analysis of donor-recipient mixed lymphocyte reactivity suggests that long-term MC may require a state of bidirectional tolerance before transfusion.
authors.affiliation: Blood Systems Research Institute, Department of Pathology, University of California, Davis, California 94118, USA. tlee@bloodsystems.org
authors.forename: Tzong-Hae
authors.initials: TH
authors.lastname: Lee
authors.forename: Teresa
authors.initials: T
authors.lastname: Paglieroni
authors.forename: Garth H
authors.initials: GH
authors.lastname: Utter
authors.forename: Daniel
authors.initials: D
authors.lastname: Chafets
authors.forename: Robert C
authors.initials: RC
authors.lastname: Gosselin
authors.forename: William
authors.initials: W
authors.lastname: Reed
authors.forename: John T
authors.initials: JT
authors.lastname: Owings
authors.forename: Paul V
authors.initials: PV
authors.lastname: Holland
authors.forename: Michael P
authors.initials: MP
authors.lastname: Busch
mesh_terms: D016913:Blood Component Transfusion; D001782:Blood Donors; D006684:HLA-DR Antigens / Q000235:genetics; D006801:Humans; D047589:Leukocyte Reduction Procedures; D007959:Lymphocyte Culture Test, Mixed; D012680:Sensitivity and Specificity; D018183:Transplantation Chimera / Q000276:immunology*; D014947:Wounds and Injuries / Q000097:blood / Q000628:therapy*
chemical_list: D006684:HLA-DR Antigens