Transfusions are the mainstay of supportive therapy in patients with aplastic anemia (AA) and may lead to anti-human leukocyte antigen (HLA) alloimmunization, thereby also increasing the risk for donor-specific antibodies in the setting of HLA-mismatched transplantation. Historically, AA patients were thought to be at particularly high risk for HLA alloimmunization.
In the past decades, blood product manufacturing (leukoreduction), but also HLA antibody testing has improved significantly by single antigen bead (SAB) technology. It is currently unknown how those developments have impacted HLA-alloimmunization and treatment outcome in patients with AA.
We retrospectively investigated 54 AA patients treated by immunosuppressive therapy and/or allogeneic hematopoietic cell transplantation after the introduction of the SAB assay at our center. We compared the HLA antibody results to a historical AA cohort (n=26), treated prior to introduction of leukoreduced blood products from 1975 to 1995.
HLA alloimmunization was detected in 43 of 54 (80%) patients in recently treated patient. Past pregnancy, female gender, disease severity, age and a history of more transfusions were significantly associated with a larger number and/or higher intensity (mean fluorescence intensity) of HLA antibodies. Treatment outcome including bleeding episodes, response to treatment, engraftment, GvHD and overall survival was not associated with HLA alloimmunization. In the historical cohort a significantly higher number of HLA antibodies (p<0.01) with a higher MFI (p<0.01) was observed.
HLA alloimmunization remains frequent in AA tested by current techniques but it has significantly decreased since prior decades and does not affect treatment outcome.

Copyright © 2021. Published by Elsevier Inc.