Acute Rejection in 6-Antigen HLA-Matched Kidney Transplant Recipients: Risk Factors and Outcomes from the Wisconsin Allograft Recipient Database (WisARD).

Acute rejection in human leukocyte antigen (HLA)-matched kidney transplant recipients is uncommon and the mechanisms involved are not well understood. Data from 6-antigen HLA-matched recipients transplanted between 1994 and 2014 were analyzed to identify the incidence, risk factors, and outcomes associated with biopsy-proven acute rejection (BPAR). A total of 278 HLA-matched recipients were identified, of which, 155 (55.8%) received a graft from a sibling donor. Ten patients (3.6%) experienced BPAR over a median follow-up of 10 years (0.41 cases per 100 person-years). Median time to rejection was 36.5 months (standard deviation ±56.4). Recipients who experienced rejection did not differ from those who did not in terms of age, gender, ethnicity, induction agent, panel reactive antibody, or sensitizing events. Acute cellular, antibody-mediated, and mixed rejection occurred in 5, 3, and 2 patients, respectively. The most common biopsy classification was Banff IA (n=4). Four out of 10 patients had documented nonadherence to maintenance immunosuppression. Thirty percent of HLA-matched recipients who rejected had graft loss and 10% died, compared to 30.8% graft loss and 28.4% deaths in non-rejectors (p=0.57 and 0.20, respectively). In conclusion, acute cellular and antibody-mediated rejection are infrequent in HLA-matched kidney transplant recipients. Nonadherence appears to be relatively common among those experiencing rejection. Acute rejection was not associated with higher graft loss or death. The pathogenesis of acute rejection in HLA-matched recipients remains to be determined.