DP reactive antibody in a zero mismatch renal transplant pair

This study describes molecular basis for positive B-cell flow crossmatch in a zero mismatch (0MM) transplant pair. Our end-stage renal disease patient was B-cell flow crossmatch positive with a 0MM deceased donor. DNA from the donor and patient were further typed by a high-resolution method. The patient's sera were tested for anti-HLA reactivity by single antigen bead using a Luminex platform. The patient and donor were found to be HLA identical except for a single DP allele MM (DPB1*0601). As there was no single antigen bead coated with DPB*0601, analysis of the amino acid residues of reactive and nonreactive DPB1 alleles was conducted. The results showed that all reactive alleles carried the amino acid D-E at residue 55 and 56 of DPB1. The MM allele DPB1*0601 also carries the DE 55-56 epitope. We conclude that positive B-cell flow crossmatch was likely the result of single MM in the DP locus.