UNCOMMON HLA ASSOCIATION IN RENAL TRANSPLANT RECIPIENTS

In renal transplantation current donor-recipient HLA-matching only considers A, B and DR antigens. Since HLA-DQ molecules are polymorphic and can elicit a humoral immune response, starting from January 2010 in the Lazio Regional Transplant Center's Laboratory, all patients waiting for a kidney transplant and all cadaveric kidney donor were typed also for these molecules. Two uncommon DRB1-DQB1 associations were found in Caucasian renal transplant candidates, routinely typed for HLA-A, -B, -DR and -DQ alleles by low-resolution PCR-SSP and/or -rSSO methods. Verification typing was performed on an independent sample by high-resolution PCR-SSP methods. Based on the haplotype frequencies in Caucasian populations, HLA Class II high resolution typing of the patients showed two uncommon associations: DRB1*11:01-DQB1*05:02 (DR11-DQ5 phenotype) in one case and DRB1*11:01-DQB1*03:02 (DR11-DQ8 phenotype) in the other. The probable Class II associations were DRB1*11:01- DRB3*03:01-DQB1*05:02-DQA1*01:02, rare in individuals of African descent, and DRB1*11:01-DRB3*02:02-DQB1*03:02- DQA1*05:05. Performing external proficiency tests, an uncommon association DRB1*08:01-DRB3*01:01 was found in a Caucasian donor. It was the first DRB1*08:01 cell typed in the UCLA International HLA DNA Exchange that had an unexpected association with DRB3*01:01 allele. A DRB1*08:01-DRB3*02:02 cell, also from a Caucasian donor, was typed previously by the DNA Exchange. The DRB1*08:01-DRB3-DQB1*04:02-DQA1*04:01 association was found in both donors. In kidney transplantation all preformed HLA antibodies have a deleterious impact on kidney graft outcome. Therefore, the presence of infrequent HLA associations emphasises the need to adopt new HLA matching criteria, including other HLA class II molecules to improve both kidney allocation and clinical graft outcome.