Immunocomplex capture fluorescence analysis for donor selection in HLA-haploidentical peripheral blood stem cell...

Donor-specific HLA antibodies (DSA) are associated with graft failure after HLA-mismatched allogeneic hematopoietic stem cell transplantation (HSCT). The most widely used method for identifying anti-HLA antibodies is the single-antigen bead (SAB) assay. Although this method has high sensitivity, it also detects natural HLA antibodies, which are considered to have low clinical significance. Instead, detection of reactivity between recipient serum and donor cells, such as lymphocyte crossmatching, may be useful for HSCT donor selection. We evaluated the efficacy of immunocomplex capture fluorescence analysis (ICFA), a highly sensitive lymphocyte crossmatching technique, as a tool for HSCT donor selection: ICFA was conducted on recipient serum and donor cells prior to HLA-haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) and transplant outcomes were evaluated. Twenty-one patients who had anti-HLA antibodies and underwent haplo-PBSCT between 2019 and 2025 were included. Patients were stratified according to DSA status into Group A (DSA-positive) and Group B (DSA-negative). Six of the seven patients in Group A and all 14 patients in Group B were ICFA-negative. The patient who was ICFA-positive with anti-HLA class I antibodies was the only patient who developed graft failure; all the patients who were ICFA-negative achieved neutrophil engraftment (except one patient in Group B who died before engraftment due to intracerebral hemorrhage), even when they were positive for DSA. Thus, ICFA may be helpful for donor selection for haplo-PBSCT patients with anti-HLA antibodies.