ANTIBODY TO HLA-DPA1*0103 IN A KIDNEY TRANSPLANT CANDIDATE.DA Youngs, Puget Sound Blood Center, Seattle, WAA non-transfused, non-transplanted, 5-parous, 60 year old woman with glomerulonephritis, was worked up for a possible living donor or cadaveric kidney transplant.The patient had no detectable HLA class I antibody, but her class II PRAs ran between 65% and 85% during the last two years.The pattern of reactivity against the screening panel was consistent, but it was not possible to assign an HLA A, B, C, DR or DQ specificity to her antibody.
The patient had positive B-cell flow cytometry crossmatches with three of her available children, and a negative crossmatch with one.After the patient had a positive crossmatch with a cadaveric donor with no HLA A, B, DR or DQ mismatches, increased effort was made to identify her antibody specificity.She was crossmatched against seven donors who had no DR or DQ mismatches with her, and with seven donors whose only DR or DQ mismatch was DQ2 (the same mismatch as her crossmatch-negative son).All these individuals had positive B-cell crossmatches.Seroligical typing of the patient confirmed that she had no unexpressed DR or DQ alleles.
As HLA DR and DQ did not appear to be the target of her antibody, the patient, her sons, and several of the DR, DQ-matched donors were typed for HLA-DPB1 and DPA1 alleles.Her two sons, one who had a positive crossmatch, the other who had a negative crossmatch, had identical DPB1 types, but different DPA1 types.The patient and the crossmatch-negative son both typed as DPA1*02 only, whereas the crossmatch-positive son was mismatched for DPA1*0103, as were the crossmatch-positive donors.Additional individuals were found who lacked DPA1*0103.Crossmatches between these individuals and the patient were negative.Along with the one son, these are the only individuals to have negative crossmatches with the patient, providing substantial proof that the patient has made antibody to HLA-DPA1*0103, an allele found in approximately 95% of Caucasians and 50% of Blacks and Asians.
This case study demonstrates the importance of typing screening panels for all HLA loci which could be the target of antibody.