How did a patient who types for HLA-B*4403 develop antibodies that react with HLA-B*4402?

This case report shows that the sensitization of a HLA-B*4403 patient by a kidney transplant with a HLA-Cw*0704 mismatch led to antibodies reacting with the 156DA eplet shared with B*4402 and other HLA-B antigens including B*0801, B*3701, B*4101, B*4201, B*4501, and B*8201. It demonstrates that antibodies induced by an HLA-C mismatch can render certain HLA-B antigens unacceptable mismatches although the patient has never been exposed to them. This finding illustrates the importance of analyzing antibody specificities against HLA epitopes in the determination of mismatch acceptability for sensitized patients.