Sensitized renal transplant recipients: current protocols and future directions

The identification of suitable donor kidneys for transplant candidates with high levels of circulating antibodies against human leukocyte antigen (HLA) is a major challenge and results in prolonged waiting times for transplantation. Technological advances in antibody characterization have permitted a more comprehensive assessment of anti-HLA antibody activity, as well as providing new insights into the clinical effect of HLA antibody class and specificity. Protocols have been developed that enable successful transplantation in patients with donor-specific antibodies (anti-HLA antibodies reactive against their donors). These protocols provide satisfactory early to intermediate-term allograft survival, and constitute an important advance in transplantation. Nevertheless, acute antibody-mediated rejection (AMR) remains a significant challenge, occurring in 20-50% of antibody-incompatible kidney transplantations. Although therapy directed toward lowering donor-specific antibody activity seems to be successful in reversing acute AMR, this condition still has an important negative impact on allograft survival. In addition, subclinical AMR seems to complicate a substantial proportion of positive-crossmatch transplantations even in the absence of allograft dysfunction, and may result in chronic histological abnormalities and shortened allograft function. New interventions for preventing acute AMR, such as anti-C5 antibody-mediated complement blockade and proteasome inhibitor-mediated plasma cell depletion, are promising therapeutic avenues currently under investigation.