Effect of preexisting human leukocyte antigen donor-specific antibodies especially human leukocyte antigen-DQ on kidney transplant outcome

Background Anti-HLA-DQ donor-specific antibodies are increasingly recognized for their role in early rejection and compromised graft function following kidney transplantation. Methods A total of 119 prospective kidney transplant recipients were evaluated for pre-transplant HLA sensitization using single antigen bead (SAB) assays for class I and class II donor-specific antibodies (DSAs). All patients had negative complement-dependent cytotoxicity (CDC) crossmatch results; however, flow cytometry crossmatch was positive for T cells in three patients and showed borderline B-cell positivity in one patient. Of these patients, 100 proceeded to kidney transplantation, including 19 ABO-incompatible transplants. All recipients were followed for a minimum of 4 years post-transplant, and induction immunosuppression was administered using either anti-thymocyte globulin (ATG) or ATLG (Grafalon ® ). Results A total of 100 patients underwent kidney transplant. Among them, 34 recipients (34%) had class I HLA antibodies (MFI range: 9,057 to 757) and 5 had class I DSAs (MFI range: 2,084 to 822) without any rejection episodes. Thirty-eight patients (38%) tested positive for class II HLA antibodies, including 20 with anti-HLA-DQ (MFI range: 7,725 to 766); of these, eight had donor-specific anti-DQ antibodies. Only one patient, who underwent an ABO-incompatible transplant and had pre-transplant DQ DSA with MFI 7,725, developed biopsy-proven antibody-mediated rejection (ABMR) but recovered following treatment. All eight DQ DSA-positive recipients showed post-transplant MFI decline within 1 month. Rejection was notably infrequent in recipients who received Grafalon ® induction. Conclusions Preformed anti-HLA-DQ DSAs, especially with MFI >5,000 and in the context of ABO incompatibility, may predispose to AMR. DQ DSAs with lower MFI require vigilant monitoring due to the risk of post-transplant rebound. ATLG-based induction was associated with low rejection incidence and favorable short-term outcomes.