INTRODUCTION: Antibody mediated rejection (AMR) is one of the main cause of loss of the kidney transplant. Despite the new BANFF classification, diagnostic difficulties and lack of prognosis factors persist. The detection of intra-graft DSA (gDSA) could be a diagnostic and prognostic tool of AMR.

METHODOLOGY: We looked for gDSA in 151 kidney graft biopsies from a monocentric, retrospective and transversal cohort of 87 sensitized recipients (sDSA+). gDSA were identified by Luminex SA assay on kidney biopsies eluates. Biopsies were reviewed and classified according to BANFF 2013 classification.

RESULTS: On 87 patients, 65 had AMR. 103 biopsies are sDSA+/gDSA+: 19 in HLA class I and 90 in HLA class II. We note a significant association of gDSA with both acute (p=0.031) or chronic (p<0.0001), with AMR histological features, in particular with C4d deposits (p<0.0001) and microcirculation inflammation (p=0.002). Patients with gDSA+ have a significantly lower graft function (p=0.045), a higher level of proteinuria (p=0.09) and a lower renal survival 4 years after the biopsy (p=0.09). A sDSA MFI > 3500 predicts the gDSA presence with a sensitivity of 70% and a specificity of 82%. Among 40 patients biopsied twice, we observed 4 cases of gDSA positivation and 4 cases of gDSA negativation. 14 patients are gDSA+/AMR- suggesting infra-histological diagnostic of AMR confirmed by histological diagnosis of AMR in 9 of the 10 patients biopsied later.

CONCLUSION: gDSA are frequently found in patients with sDSA; they are a witness of the interaction between sDSA and the graft endothelium. They could represent an additional argument for AMR diagnosis and could have a prognosis value that should be confirmed by a prospective study.

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