A novel approach reveals that HLA class 1 single antigen bead-signatures provide a means of high-accuracy pre-transplant risk assessment of acute cellular rejection in renal transplantation.

BACKGROUND: Acute cellular rejection (ACR) is associated with complications after kidney transplantation, such as graft dysfunction and graft loss. Early risk assessment is therefore critical for the improvement of transplantation outcomes. In this work, we retrospectively analyzed a pre-transplant HLA antigen bead assay data set that was acquired by the e:KID consortium as part of a systems medicine approach. RESULTS: The data set included single antigen bead (SAB) reactivity profiles of 52 low-risk graft recipients (negative complement dependent cytotoxicity crossmatch, PRA < 30%) who showed detectable pre-transplant anti-HLA 1 antibodies. To assess whether the reactivity profiles provide a means for ACR risk assessment, we established a novel approach which differs from standard approaches in two aspects: the use of quantitative continuous data and the use of a multiparameter classification method. Remarkably, it achieved significant prediction of the 38 graft recipients who experienced ACR with a balanced accuracy of 82.7% (sensitivity = 76.5%, specificity = 88.9%). CONCLUSIONS: The resultant classifier achieved one of the highest prediction accuracies in the literature for pre-transplant risk assessment of ACR. Importantly, it can facilitate risk assessment in non-sensitized patients who lack donor-specific antibodies. As the classifier is based on continuous data and includes weak signals, our results emphasize that not only strong but also weak binding interactions of antibodies and HLA 1 antigens contain predictive information. TRIAL REGISTRATION: ClinicalTrials.gov NCT00724022 . Retrospectively registered July 2008.

Assessment of In Vivo Kidney Cell Death: Acute Kidney Injury.

The kidney has been studied as an organ to investigate cell death in vivo for a number of reasons. The unique vasculature that does not contain collateral vessels favors the kidney over other organs for the investigation of ischemia-reperfusion injury. Unilateral uretic obstruction has become the most prominently studied model for fibrosis with impact far beyond postrenal kidney injury. In addition, the tubular elimination mechanisms render the kidney susceptible to toxicity models, such as cisplatin-induced acute kidney injury. During trauma of skeletal muscles, myoglobulin deposition causes tubular cell death in the model of rhabdomyolysis-induced acute kidney injury. Here, we introduce these clinically relevant in vivo models of acute kidney injury (AKI) and critically review the protocols we use to effectively induce them.

Assessment of In Vivo Kidney Cell Death: Glomerular Injury.

The glomerulus functions as the filtration unit of the kidney. The mesangial, endothelial, and podocyte cells of the glomerulus exhibit the three clinically most important cell types, which are involved in diverse pathologic processes. Cell death has hardly been investigated in these cells but may be of critical importance to the pathogenesis of nephrotic syndrome, nephritic syndrome, focal segmental glomerulosclerosis (FSGS), mesangial proliferation, and thrombonic microangiopathy (which involves dysfunction and death of glomerular endothelial cells). The complexity of the glomerulus is frequently affected in autoimmune disorders, which may elicit cell death in mesangial cells and glomerular endothelia. Artificial antisera are used to induce anti-mesangial cell serum-induced mesangiolysis and selective endothelial cell injury, respectively. Genetic variations result in loss of function of podocytes and nephrotic syndrome, which may encompass similar cell death mechanisms as the ones that are observed in the model of secondary focal segmental glomerulosclerosis (FSGS). The following protocols describe our current arsenal to target glomerular cells in vivo.