A substantial proportion of patients with recurrent implantation failure treated with partner lymphocyte immunotherapy achieved live birth within 3 years after immunization

Objective: In the 1980s, the immunotolerance-inducing effect of leukocytes in blood products was observed, and our department started using partner lymphocyte immunotherapy (LIT) for patients experiencing recurrent miscarriage. We also used LIT for couples with unexplained infertility who had undergone at least three unsuccessful embryo transfers. The aim of this study was to analyze the live birth rate after LIT in our patient cohort with recurrent implantation failure. Methods: From 2017 to 2022, we conducted a prospective, noninterventional, observational study of patients who received a questionnaire two to 3 years after LIT. We also performed T- and B-cell crossmatches, human leukocyte antigen (HLA) typing, and complement-dependent cytotoxicity assays. Results: We sent questionnaires to 475 couples with unexplained infertility and received 268 responses. A total of 157 live births (58.6%) within 3 years of LIT were reported. We identified a higher proportion of HLA-crossmatch-positive cases in the live birth group (71.8%) than in the group without live births (59.5%). The median age was 34 years in the live birth group and 36 years in the group without live births. We observed no significant influence of additional therapies including immunoglobulins, corticosteroids, anticoagulants, granulocyte colony-stimulating factor, or lipid infusions. Conclusion: In our patient cohort with at least three previous unsuccessful embryo transfers, we observed a substantial proportion of patients who achieved a live birth within three years after LIT. An individualized treatment decision is required for each patient, as the efficacy of LIT in patients with unexplained infertility must be confirmed in a future controlled, randomized study.