De novo DQ donor-specific antibodies are associated with a significant risk of antibody-mediated rejection and transplant glomerulopathy.

Background: The importance of human leukocyte antigen (HLA) matching in renal transplantation is well recognized, with HLA-DR compatibility having the greatest influence. De novo DQ donor-specific antibodies (DSAbs) are the predominant HLA class II DSAb after transplantation. The aim of this study was to establish the incidence and outcomes after the development of DQ DSAbs along with the impact of class II HLA mismatch on their development.

Methods: We retrospectively analyzed 505 patients who received a renal-alone transplant between 2005 and 2010. We excluded patients who received an ABO- and HLA-incompatible allograft, which we defined as those with a positive crossmatch or preformed DSAbs detected by single-antigen beads only.

Results: Of 505 patients, 92 (18.2%) developed DSAbs, with 50 (54.3%) of these 92 patients having DQ DSAbs. Patients who developed DQ DSAbs were at significant risk for antibody-mediated rejection, transplant glomerulopathy, and allograft loss (P<0.0001). Of 505 patients, 108 (21.4%) were matched at both the DR and DQ loci, 284 (56.2%) were mismatched at both loci, 38 (7.5%) were matched at DR alone, and 75 (14.9%) were matched at DQ alone. Patients mismatched at both DR and DQ were at risk for developing class II DSAbs when compared with those mismatched at either DR or DQ alone, P=0.001, and were at risk for antibody-mediated rejection, P=0.001.

Conclusions: DQ DSAbs are associated with inferior allograft outcomes. This study shows the importance of establishing the DQ match before transplantation to define immunologic risk.