Clinical impact of preformed donor-specific denatured class I HLA antibodies after kidney transplantation

Class I single-antigen flow beads (SAFB) carry native and denatured human leukocyte antigen (HLA) molecules. Using a cohort of 179 class I HLA-sensitized kidney recipients, we described incidence and clinical relevance of preformed denatured HLA donor-specific antibodies (DSA) using two different assays: an acid-treated SAFB assay (anti-dHLA DSA) and the iBeads assays (SAFB+/iBeads- DSA). Eighty-five class I DSA were found in 67 patients (median mean fluorescence intensity [MFI] of 1729 [range 520-13882]). Anti-dHLA and SAFB+/iBeads- DSA represented 11% and 18% of class I DSA and were mainly low MFI DSA (500-1000 MFI). Concordance between these two assays was good (90%). None of the patients with only class I anti-dHLA DSA or only SAFB+/iBeads- DSA developed acute clinical antibody-mediated rejection in the first-year post-transplantation, and their five-yr death-censored graft survival was similar to that of patients without DSA. Moreover, all these patients displayed a negative current T-cell flow cytometry cross-match. Therefore, both anti-dHLA DSA and SAFB+/iBeads- DSA appear irrelevant, which could explain the good outcome observed in some patients with preformed class I DSA.