Detection of donor-specific HLA antibodies before and after removal of a rejected kidney transplant.

UNLABELLED Serum analysis of patients considered for retransplantation has a potential limitation that the rejected allograft may absorb HLA antibodies. We have determined how the highly sensitive micro bead-based Luminex antibody-binding assay with single antigens can detect donor-specific HLA antibodies (DSA) in patients before and after surgical removal of a rejected allograft. This analysis was done for 65 allograft nephrectomy (allonx) cases contributed by 16 laboratories worldwide. In the HLA-A,B and -DRB1 mismatch categories the incidence of DSA reactivity pre-allonx and post-allonx was 64% vs 87% (p=0.0033) and 57% vs 86% (p=0.001), respectively. The frequencies of individual reactive antigens were also lower before allonx: for HLA-A,B antigens: 49% vs 75% (p<0.0001) and DRB1 antigens: 48% vs 79% (p=0.0001). On the other hand, no significant differences were seen between the pre-allonx and post-allonx frequencies of DSA to DRB3/4/5 (65% vs 78%, p=0.22) and DQ mismatches (76% vs 87%, p=0.18). CONCLUSION although the sensitive Luminex antibody assay can detect anti-donor antibodies in the presence of a rejected transplant, it is apparent that the antibody specificity pattern is often incomplete especially against the HLA-A, -B and DR mismatches. This understanding seems relevant to the determination of acceptable mismatches for patients considered for retransplantation.