P085 Heat map of HLA antibody profiles in 5281 kidney wait list candidates revealed locus/CREG/bead-specific patterns associated with mode of sensitization

Abstract

Aim To assess the nature of HLA antibody (Ab) profile in kidney transplant (tx) candidates. Method Kidney waitlist candidates (n = 5281) were tested for 123 distinct HLA Ab using One Lambda single antigen beads on DTT-treated sera. Mean fluorescence intensity (MFI) of all detected Ab were used to generate heat map and Ab patterns were compared with several conditions. Results Figure shows the heat map of HLA Ab in sensitized patients with CPRA >20%. As expected, the Ab producers are more common in re-tx group and produce high MFI (>10 K) Ab to DQ (47% vs. 4%), DP (21% vs. 3%) and A (37% vs. 8%) antigens compared to 1st-tx group. In the re-tx group, females are frequent producers of Ab to HLA-B, C, DR and A1 and A2 CREGs, while males are frequent producers of Ab to DQ, DP and A10 CREG. High MFI (>10 K) DQ Ab producers are more common in re-tx males, which is consistent with the fact that the de novo donor-specific antibodies produced post-tx are frequently DQ-specific. In the 1st-tx candidates, females are frequent Ab producers and common Abs are directed to HLA-B, DR and A1 & A2 CREGs. The composite MFI of 1st-tx females and males have a median of 16 K and 6 K, respectively. The most frequent Abs that occur in >4% of 1st-tx males are weakly reactive (MFI DQ7 > B44 > B82 > DP1 > B45 > B57 > A66 > DP11 > A80 > Cw15. These weak Abs are also seen frequently in 1st-tx females. No association was observed between these weak reactions and candidates’ transfusion history, age, race, primary disease, blood group & HLA types, suggesting cryptic epitope reactivity of these beads. The most frequent Ab in all sensitized patients is B76 (1.5%). The most frequent Ab in sensitized patients per locus is A25 (6.4%), B76 (2.8%), Cw15 (11.5%), DR9 (9%), DQ7 (19.4%) and DP6 (7.7%). Conclusions Weak Ab detected frequently in 1st-tx males are likely directed to cryptic epitopes and require additional scrutiny including screening by another reagent. High frequency of MFI > 10 K DQ Ab in re-tx males suggest the need for DQ matched tx. Download : Download high-res image (891KB) Download : Download full-size image