HLA-specific platelet trasfusion as part of desensitization strategy in patients with donor-specific anti-HLA antibodies before stem cell transplantation.

The presence of donor-specific anti-HLA antibodies (DSAs) in patients who are candidates for allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a recognized risk factor for delayed engraftment and mortality. In the absence of an alternative donor, patient desensitization is indicated to reduce or eliminate DSAs; however, harmonization among transplant centers remains insufficient and reduction of DSAs is sometimes unsuccessful. Here, we present the feasibility and results of our recent monocenter experience on nine immunized HLA class I DSA+ patients undergoing pre-transplant desensitization using HLA-specific platelet transfusion, as a means of antibody adsorption through platelets expressing the same HLA specificities targeted by DSAs. All allo-HSCTs were from HLA-mismatched donors, both unrelated or related haploidentical. The approach appeared safe for donors and patients and potentially useful in mitigating the detrimental impact of class I DSAs, with successful engraftment observed in two of four patients with MFI > 10,000 and in all patients with MFI <10,000. Until harmonized and more risk-adapted desensitization strategies become available, sharing inter-center experiences between clinical and transfusion units will likely improve the management of hyperimmunized patients and enhance the availability of emerging desensitizing strategies.