Posttransplant Allosensitization in Low Immunological Risk Kidney and Kidney-Pancreas Graft Recipients

INTRODUCTION Posttransplantation allosensitization prevalence and effect on kidney grafts outcomes remain unsettled. METHODS Between 2007 and 2012, 408 patients received a primary kidney graft (with 68 patients also receiving a pancreas graft) after a negative cytotoxic crossmatch. All patients had a pretransplant negative anti-HLA screening and 0% panel reactive antibodies. We analyzed retrospectively the results of anti-HLA antibodies screening by Luminex assay, performed between 6 and 24 months after transplant, and searched for the risk factors for antibody positivity and its impact on kidney graft outcomes. RESULTS Anti-HLA antibodies prevalence at 6 months was 17.4%. Previous steroid-insensitive acute rejection was the only risk factor for both anti-HLA classes detected antibodies. Antithymocyte globulin induction was also a risk factor for anti-HLA-I antibodies. Antibody positivity status was associated with reduced graft function at 12 months and graft survival at 5 years (91.5% versus 96.4%, P = 0.03). In multivariable Cox analysis, delayed graft function (HR = 6.1, P < 0.01), HLA mismatches >3 (HR = 10.2, P = 0.03), and antibody positivity for anti-HLA class II (HR = 5.1, P = 0.04) or class I/II (HR = 13.8, P < 0.01) were independent predictors of graft loss. CONCLUSIONS Allosensitization against HLA class II ± I after transplant was associated with adverse kidney graft outcomes. A screening protocol seems advisable within the first year in low immunological risk patients.