A Comparison of Intra-Operative Human Leukocyte Antigen Antibody Removal Techniques in Pediatric Heart Transplantation

Abstract

Many potential pediatric heart transplant (HT) recipients develop sensitization to potential donor Human Leukocyte Antigens (HLA) from prior tissue and blood product exposure. HT in the face of allosensitization carries elevated risk of morbidity and mortality. We sought to determine and compare the degree and timing of HLA-antibody removal between centrifuge-based plasmapheresis (cPP) and membrane-based plasmapheresis (mPP) during cardiopulmonary bypass (CBP). Two mPP and two cPP systems were each incorporated into CPB circuits. The prime consisted of highly sensitized pooled donor whole blood. Blood was considered sensitized if any HLA-antibody exceeded 3000 mean fluorescence intensity (MFI) units by Luminex assay. Fresh frozen plasma was utilized to replenish the plasmapheresis circuits. Samples to determine the panel reactive antibody (PRA) were taken at baseline, then at 30 minute intervals until the end-point at 2 hours. The pooled donor blood was sensitized to HLA Class II but not Class I per institutional threshold. Reduction of anti-HLA class II antibody to below threshold levels (MFI <3000) was achieved in both the cPP and mPP systems. In the cPP circuits, there was a gradual decrease in antibody levels at each 30-minute interval, reaching a nadir at 90 minutes with a 2 to 3.5-fold reduction at completion. In the mPP circuit, there was an initial rapid decrease in antibody levels at 30-minute mark followed by a plateau corresponding to a 1.7 to 2.5-fold decrease in MFI at 2 hours. The incorporation of cPP or mPP systems into the CPB circuit can effectively reduce circulating HLA-antibodies. This can be accomplished within the time period of CPB for implantation before graft reperfusion and may be done more efficiently using cPP. This technology may have important utility for sensitized transplant recipients at increased risk for early antibody-mediated rejection.