Rebound and overshoot of donor‐specific antibodies to human leukocyte antigens (HLA) during desensitization with plasma exchanges in hematopoietic progenitor cell transplantation: A case report.

Background: Donor‐specific antibodies (DSA) to HLA have been associated with graft loss in hematopoietic progenitor cell (HPC) transplantation. Limited data associate therapeutic plasma exchange (TPE) with desensitization and successful engraftment. We report an attempt of desensitization and observed overshooting of DSA during transplantation. Case report and results: A 27‐year‐old female with cutaneous T cell lymphoma was scheduled for HPC transplantation from her HLA‐haploidentical half‐sister, who carried the HLA‐DRB1*13:03:01 allele. The patient had the corresponding DSA. Lacking an alternative donor option at the time, we attempted a desensitization approach by immunosuppression with tacrolimus and mycophenolate mofetil (MMF). Unexpectedly, DSA increased from a mean fluorescence intensity (MFI) of 1835 on day −63 to 9008 on day −7. The MFI increased further during 3 TPE procedures and intravenous immunoglobulin (IVIG) until day −1. After transplantation, the DSA remained elevated despite 2 more TPE/IVIG procedures and graft‐versus‐host disease prophylaxis with high‐dose cyclophosphamide, sirolimus, and MMF. Flow cytometric crossmatch, initially negative, turned positive after transplantation. Primary graft failure occurred and was attributed to antibody‐mediated rejection. A second transplantation from a 7/8 HLA‐matched unrelated donor, not carrying DRB1*13:03 allele, resulted in successful engraftment. Conclusion: Unexpected and rapid increases of a DSA can occur despite the use of current desensitization approaches. This is problematic when conditioning has already started, as such increases are unlikely to be overcome by TPE or other interventions for desensitization. Overshoot of DSA in HPC transplantation has rarely been reported. Its cause remains unclear and can include underlying disease, immunotherapy, chemotherapy, or TPE. [ABSTRACT FROM AUTHOR]