IDENTIFICATION OF PATIENTS AT HIGH RISK OF GRAFT LOSS BY PRE- AND POSTTRANSPLANT MONITORING OF ANTI-HLA CLASS I IgG ANTIBODIES BY ENZYME-LINKED IMMUNOSORBENT ASSAY

Abstract

Identification of risk factors influencing graft survival may lead to the development of models to predict graft outcome. Such models may provide guidance for immunosuppressive therapy, measure posttransplantation outcome, and eventually improve graft survival in high-risk patients. A major risk factor influencing graft survival is allosensitization. However, due to the lack of standardization of lymphocytotoxicity assays, the detection of alloantibodies utilizing this current methodology may not correlate with posttransplant events. Recently, a novel standardized enzyme-linked immunosorbent assay (ELISA) for the detection of anti-HLA class I IgG antibodies was developed. To evaluate the predictive value of this diagnostic test, a retrospective analysis of 124 renal allograft recipients with an 18-month follow-up time was performed. A highly significant (P=0.01) correlation between pre-transplant ELISA panel reactive antibody (PRA) results and graft loss was observed. Patients with pre-transplant ELISA PRA of >10% had a three times higher risk of graft loss compared with patients who tested negative. No such correlation was observed with complement-dependent cytotoxicity results independent of the reduction of IgM antibodies with dithiothreitol. Similarly, a highly significant correlation of ELISA results with the occurrence of early graft dysfunction was observed. Almost all patients (88%) with a pretransplant ELISA PRA of >50% required posttransplant dialysis, compared with 45% of patients with a pretransplant ELISA PRA of 10-50% and 27% of patients with a pretransplant ELISA PRA of <10%. No such difference was observed with complement-dependent cytotoxicity %PRA values. Analysis of posttransplant specimens by ELISA demonstrated a strong correlation of assay results with graft rejection and graft dysfunction. In summary, these results suggest that detection of anti-HLA class I antibodies by ELISA identifies patients at high risk for graft loss. No other single risk factor of such magnitude has been identified so far.

The clinical significance of conversion of complement-dependent cytotoxic T cell crossmatch test after renal transplantation

“…Similar results were published by Monteiro et al [14], who monitored preand post-transplant PRA levels by ELISA. They showed that the rise of PRA after transplantation was a deleterious sign and suggested that these patients were immunologically high responders.…”

The Evaluation of the Renal Transplant Candidates: Clinical Practice Guidelines

“…Newer assays, utilizing more sensitive methods, e.g. enzyme-linked immunosorbent assay (ELISA) and Flow Bead, and using specific HLA antigens as targets have been introduced to identify antibodies specific to HLA antigens (1094)(1095)(1096)(1097)(1098)(1099). Knowing whether there are antibodies specific to HLA antigens helps in correctly interpreting the crossmatch results.…”

“…Recently, newer assays have been introduced that use more sensitive methods (ELISA and Flow Bead), and use specific soluble HLA target antigens immobilized in tray wells or on microbeads, to identify sera with IgG antibodies to HLA antigens (1094)(1095)(1096)(1097)(1098)(1099). Results from the ELISA-PRA have been shown to be more predictive of a posttransplant acute rejection and graft loss than the membrane dependent AHG-PRA assay (1094)(1095)(1096)(1097)(1098).…”

“…Results from the ELISA-PRA have been shown to be more predictive of a posttransplant acute rejection and graft loss than the membrane dependent AHG-PRA assay (1094)(1095)(1096)(1097)(1098). The Flow Bead PRA (Flow PRA) procedure can detect IgG antibody to HLA antigens in sera that are reported to be non-reactive (0% PRA) by ELISA (1093).…”

Flow cytometry PRA using lymphocyte pools from random donors

“…The specificities of Abs and the frequency of target lymphocytes that will react to a serum are determined after the analysis of positive reactions in each individual well (4).…”