Preformed HLA-DQ Donor-Specific Antibodies: Distinct Immunological Characteristics and Clinical Implications in Kidney Transplantation.

The aim of this study is to characterise the immunological features of preformed HLA-DQ DSAs and investigate their impact on post-transplant outcomes. Among 1540 ABO-compatible KT recipients with available high-resolution HLA typing at Seoul St. Mary's Hospital (January 2010-December 2024), 179 had preformed DSAs. Patients were classified into DQ group (n = 58), comprising those with DQ DSAs alone or in combination with other DSAs, and non-DQ (n = 121) group. We compared baseline DSA characteristics, desensitisation (DSZ) responses and post-transplant outcomes. The DQ group had a significantly higher proportion of re-transplant recipients. At baseline, DQ DSAs exhibited markedly higher MFI values compared to non-DQ DSAs. Following DSZ, 45.2% of DQ DSAs remained strong (MFI > 10,000), compared to only 2.8% of non-DQ DSAs. While the overall incidence of acute ABMR did not differ significantly between groups, a significant difference was observed in the temporal distribution and the characteristics of the associated DSAs. In early-onset ABMR, cases in the DQ group developed after the complete resolution of preformed DSAs, whereas those in the non-DQ group were associated with preformed DSAs. Late-onset ABMR occurred more frequently in the DQ group (41.7% vs. 10.0%, p = 0.024), and it developed with preformed DQ DSAs. Furthermore, allograft function showed a more rapid deterioration in the DQ group. Preformed DQ DSAs carry a higher immunological risk and exhibit greater resistance to treatment than non-DQ DSAs, and tend to cause late-onset acute ABMR rather than immediate post-transplant rejection. Therefore, more stringent immunological monitoring and immunosuppressive therapy are required.