Anti-Human Leukocyte Antigen Antibody Detection from Terasaki’s Humoral Theory to Delisting Strategies in 2024

The human leukocyte antigen (HLA) system plays a critical role in transplant immunology, influencing outcomes through various immune-mediated rejection mechanisms. Hyperacute rejection is driven by preformed donor-specific antibodies (DSAs) targeting HLAs, leading to complement activation and graft loss within hours to days. Acute rejection typically occurs within six months post-transplantation, involving cellular and humoral responses, including the formation of de novo DSAs. Chronic rejection, a key factor in long-term graft failure, often involves class II DSAs and complex interactions between the innate and adaptive immune systems. Advancements in HLA antibody detection, particularly single antigen bead (SAB) assays, have improved the sensitivity and characterization of DSAs. However, these assays face challenges like false positives from denatured antigens and false negatives due to low antibody titers or complement competition. Furthermore, molecular mismatch (MM) analysis has emerged as a potential tool for refining donor–recipient compatibility but faces some issues such as a lack of standardization. Highly sensitized patients with calculated panel-reactive antibodies (cPRA) of 100% face barriers to transplantation. Strategies like serum dilution, novel therapies (e.g., Imlifidase), and delisting approaches could refine immunological risk assessment and delisting strategies are essential to expand transplant opportunities for these patients.