Absence of transfusion-associated microchimerism in pediatric and adult recipients of leukoreduced and gamma-irradiated blood components

BACKGROUND: Transfusion‐associated microchimerism (TA‐MC), the persistence of significant levels of donor white blood cells (WBCs) in blood recipients for prolonged periods, has been demonstrated after nonleukoreduced and leukoreduced transfusion to patients with severe traumatic injury. Development of TA‐MC has not been rigorously studied in settings that do not involve massive trauma where the blood is leukoreduced and irradiated. STUDY DESIGN AND METHODS: A cohort of 409 prospectively followed medical and surgical adult and pediatric female recipients of leukoreduced and mostly irradiated allogeneic red blood cell and platelet transfusions were evaluated to determine development of TA‐MC. Four‐ and 8‐weeks‐posttransfusion samples were analyzed using quantitative real‐time polymerase chain reaction for Y‐chromosome sequences in WBC DNA, the marker for microchimeric cells in female blood recipients. Repeat testing was performed on Y‐chromosome–positive samples to confirm microchimerism (MC), and subsequent posttransfusion samples were tested to investigate persistence of MC. RESULTS: On initial testing, 40 of 207 (19%) adult and 44 of 202 (22%) pediatric female blood recipients demonstrated low‐level MC. On repeat testing of these and additional specimens, 12 (3%) recipients demonstrated low‐level transient MC, but none had persistent TA‐MC similar to that seen in transfused trauma patients. CONCLUSION: Persistence of MC was not demonstrated in adult and pediatric recipients of leukoreduced and mostly irradiated blood components. The risk of TA‐MC appears to be dependent on the clinical setting and is rare other than in patients sustaining severe traumatic injury.