Detection and analysis of HLA class I specific alloantibodies in the sera of sensitised dialysis recipients waiting for kidney retransplantation.

Background. Almost all patients who rejected a kidney graft displayed anti-HLA antibodies (Abs), and de novo development of anti-HLA Abs in transplanted patients has been identified as a risk factor for both acute and chronic rejection. The aim of this study was to evaluate the specificities of anti-HLA class I Abs detected in the sera of alloimmunised patients waiting for a kidney retransplantation. Methods. Kidney recipients (n = 62; male/female: 42/20; age: 43 ± 18 years) on waiting list for kidney retransplantation (52 for a second and 10 for a third transplant) were enrolled during 2002-2004 for HLA Abs screening. Among these kidney recipients, 50 who displayed persistently a panel reactive antibody (PRA) values >10% were selected and analysed for Abs specificity. Abs detection was performed by using complement dependent cytotoxicity technique and subsequently by ELISA to confirm or define better the % PRA and anti-HLA class I specificity. The specificities of anti-HLA Abs were classified as private, public, or multispecific. Results. In 35 patients (70%) only Abs directed against private HLA class I specificities were found. These Abs were expressed by graft donors in 33 cases. In this group, PRA ranged from 20% to 60%. In 12 patients (24%), Abs directed against public epitopes belonging to cross reactive groups (CREG) or an association of anti-private and anti-public Abs occurred, with a PRA ranged from 25% to 90%. Three patients showed multispecific Abs with %PRA >80%. Conclusions. The results of these study indicate that in the majority of donor-recipient pairs the immunogenic determinants were private specificities of mismatched HLA-A and B antigens, whereas in a lesser extent public CREG epitopes were found. Only in three patients no anti-HLA class I specificities were determined, as they displayed multispecific Abs. These findings may lead to improve donor-recipient matching in dialysis recipients waiting for kidney retransplantation.