ANTI-DONOR DR103 IMMUNIZATION IN A DRB1*0101 KIDNEY ALLOGRAFT RECIPIENT.

Abstract

P11 Aims: Molecular biology techniques have improved our knowledge on HLA genomic polymorphism, especially on class II polymorphism. We provide evidence that a DRB1*0101 kidney allograft recipient can immunize against a DR103 antigen carried by the graft. Methods and results: A 47-year-old woman received a cadaveric kidney allograft on February 1991. HLA recipient phenotype, determined by serological method, was A2 B44 B62 DR1 DR4 and HLA donor phenotype was A2 B15 B35 DR1 DR2. Chronic allograft nephropathy lead to allograft failure on December 1997. A retrospective study of circulating HLA antibodies using flow cytometry identified anti-HLA DR103 three weeks after allograft nephrectomy. Anti-DR103 antibodies were also identified with flow cytometric assay in eluates of the removed kidney. These data and the availability of HLA molecular typing lead us to control donor and recipient tissue typing performed by serological methods. Using molecular biology (PCR-SSP primer), class II donor HLA genotype was DRB1*0101, 0103 and recipient genotype was DRB1*0101, 04. Furthermore the husband and one daughter of the propositus also carry the class II allele DRB1*0103. Conclusions: HLA class II genomic polymorphism has been precised by molecular biology techniques. At least eight DRB1*01 alleles are currently recognized. DRB1*0101 is the most common allele in Caucasians. DRB1*0103 is an uncommon allele associated with inflammatory bowel diseases. DRB1*0103 differs from DRB1*0101 by six base pairs clustered in the third variable region of the second exon, leading to three amino acids changes in the β chain of the HLA DR molecule. Despite these only three amino acids replacement we observed an alloimmunization against DR 103 antigen in a DRB1*0101 recipient. DRB1*0103 was identified in the patient’s husband and one out of their children, thus suggesting a presensitization to this antigen during pregnancy and a second set reaction induced by the transplant carrying this antigen. The deleterious role of the anti DR 103 antibody found in both serum samples and eluates of the removed kidney is retrospectively probable in the graft loss.