LBP22: STRONG DONOR SPECIFIC ANTI-HLA DR53 ANTIBODY DETECTED BY SINGLE-ANTIGEN BEADS SHOULD NOT ALWAYS PREVENT TRANSPLANTATION

Abstract

Background Donor-specific antibodies towards HLA-DR51/52/53 were reported both as risk factors for allograft rejection, and as specificities with poor response to desensitization therapy. Here we present a case with strong antibody towards HLA-DR53 who was successfully transplanted. Case study. 47-year-old male renal transplant candidate with cPRA of 68%, was repeatedly detected with anti-HLA DR53 antibodies by Luminex single-antigen beads. HLA-DR53 was a mismatched antigen for his potential living donor (Table 1). Antibody IgG strength for a-HLA DR53 ranged between 7500 and 10000 MFI over one-year period. At these MFI values, our lab usually expects a positive cytotoxic B-cell crossmatch, or at least a positive B-cell flow crossmatch. However, both cytotoxic and flow crossmatches with his living donor were negative. To address this issue, we tested the living donor with other two sera known for a-HLA DR 53 activity, both in neat, and 1:4 and 1:8 dilutions, by flow crossmatch. All these combinations provided positive results of > 180 MCS above cutoff (1024 scale). Alternatively, candidate recent and peak sera was flow crossmatched with other two HLA-DR 53 cells, giving again negative results. Under the hypothesis of cryptic epitope DR53 reactivity, we also tested candidate sera with Luminex beads of different antigenic source (mixed and PRA), which have shown no DR53 reactivity. Under these circumstances, we concluded that the virtual crossmatch between the transplant candidate and his living donor was negative. Post transplant monitoring shows no signs of rejection at one year of follow-up. Conclusion Although solid-phase methods for antibody detection became mandatory in renal transplantation, a combination of technologies, rather than a single one, would be more adequate for antibody detection and identification. Table 1 ABO A B C DR DRw DQ DP Patient B 1 80 71 72 2 7 11 8 52 7 0301 0101 Donor 1 B 2 23 27 51 1 2 11 4 52 53 7 8 0401