Antibody-mediated rejection after alemtuzumab induction: incidence, risk factors, and predictors of poor outcome.

Background: Antibody-mediated rejection (AMR) is associated with allograft loss. Identification of factors associated with poor outcome has not been extensively studied.

Methods: We retrospectively studied 469 patients who received a negative crossmatch renal transplant with alemtuzumab induction. Forty-eight of 469 (10.2%) patients were treated for AMR. Thirty of 48 (62.5%) of the cases fulfilled the Banff criteria for definite AMR, whereas 18 of 48 (37.5%) were categorized as suspicious for AMR (tissue injury with C4d staining or donor-specific antibodies [DSAbs]). Sensitization, high human leukocyte antigen, and -DR mismatch were risk factors for the development of AMR (P = 0.0016, 0.001, and 0.012, respectively).

Results: Allograft survival was inferior in the AMR group (70.2%) compared with the nonrejector group (97.0%) (P<0.001). Forty-two of 48 (87.5%) of patients with acute AMR had DSAbs. Patients with CII DSAbs at the time of AMR, whether alone or in combination with CI DSAbs had the worst allograft survival (P = 0.014). Both the mean cumulative and immunodominant mean fluorescence index were higher in those patients who subsequently lost their grafts (P<0.001). Patients with diffuse C4d staining had inferior allograft survival than those with focal C4d or no staining (P = 0.02). There was no significant difference in survival by histological grade but a trend to inferior outcomes in those with vascular involvement (P = 0.06). Those patients who met the full Banff criteria had worse survival than those with suspicion for AMR only (P = 0.04).

Conclusion: This study identifies patients at risk of graft failure from AMR. These patients may benefit from newer therapeutic strategies including the use of eculizumab or bortezomib.