Identification of HLA Class I specific alloantibodies in sensitized dialysis recipients waiting for a kidney retransplantation.

Background - The goal of this study was to evaluate the antibody specificity of anti-HLA class I antibodies (Ab) detected in the sera of alloimmunized patients (Pts) waiting for a kidney retransplantation (AP-WKRTx). Methods - The study group consisted of 56 potential transplant recipients showing a panel reactive antibody values (PRA) >5%. Ab detection was performed in parallel by using two techniques: Complement-Dependent Cytotoxicity (CDC) and ELISA. The HLA Ab specificities were classified as either a private specificities and/or cross-reactive group (CREG) public epitopes. Results - Pts were identified according to their immunization extent as follows: I) Group I: n=13 Pts (21.4% of the total) with a PRA between 6% and 25%. In this group, no specific HLA Ab were detected. ii) Group II: n=40 Pts (71.4%) with PRA ranging from 26% to 60%. In this group, 27 Pts showed Abs anti-a single private HLA specificity, without evidence of anti-CREG Abs, whereas 9 Pts had anti-CREG Abs with or without antiprivate HLA specificities. iii) Group III: n=3 Pts (5.4%) with a PRA >60%, and multiple Ab against a large series of non-characterized HLA determinants. The most frequent private HLA class I specificities detected by Abs were: a) for A Locus (A1-A3, A23, A24, A26); b) for B Locus (B7, B51,B44,B18, B49). Conclusions - These results indicate that for the majority of donor-recipient pairs, the immunogenic determinants mainly involved in HLA class I specific production are private specificities, and only in a lesser percentage by CREG epitopes. These findings may have important implications to improve donorrecipient matching in AP-WKRTx.