HLA and MICA: Targets of Antibody-Mediated Rejection in Heart Transplantation

Background. The goal of this study was to determine whether antidonor antibodies directed against human leukocyte antigen(HLA) or endothelial cells (ECs) expressed antigens, including major histocompatibility complex class I chain-related antigens A (MICA) are associated with the diagnosis of antibody-mediated rejection (AMR) in heart transplant recipients. Methods. We studied posttransplant antidonor HLA antibodies in 168 heart allograft recipients transplanted from October 2001 to December 2005. Among them, there were 37AMR+ patients and 131 age-and sex-matched AMR- controls. Sera were collected at the time of protocol biopsies and tested for the presence of HLA antibodies. Seventy-two of the 168 patients were genotyped for donor and recipient MICA alleles and were tested for the presence of anti-MICA antibodies. Thirty-one patients who never developed antibodies to HLA or MICA were further tested for anti-EC antibodies. Results and Conclusions. Of 37 AMR+ patients, 22 (60%) developed donor-specific antibodies (DSA) to HLA compared with 6 of 131(4%) AMR- patients (P < 0.0001). Of the remaining 15AMR+ patients, 5 had anti-HLA antibodies that were not donor specific and 10 did not show any HLA antibodies. In the subgroup of 72 patients, all 19 AMR+ patients had clearly demonstrable antibodies reactive with donor HLA, MICA or with nondonor-derived ECs, with 30% of them showed antibodies directed to non-HLA antigens. The incidence of transplant coronary artery disease was significantly higher in patients who had DSA to HLA and MICA compared with patients without DSA.