Introduction: Antibody-mediated rejection (AMR) is the main cause of graft loss, but current guidelines only recommend optimization of immunosuppression in late AMR (>30 days post-transplantation). This study assesses the effectiveness of treatment in late AMR, as well as the responses between clinical rejections and those detected by protocol biopsy.

Materials and Methods: Retrospective cohort of kidney transplant recipients with AMR under follow-up at the INCMNSZ and the “CMN20 de Noviembre”, between January 2011 and March 2021. Chi square and Student's T or Mann-Whitney U were used according to their distribution. Spearman’s correlation was used. A p <0.05 was considered significative.

Results: 180 patients were analyzed, 57.2% women, average age 35.9 years, 65.6% living donor, 33% received Thymoglobulin as induction and 66.7% received prednisone, mycophenolate and tacrolimus. 95% were late AMR. 65% detected with protocol biopsy. Class II DSA predominated. The evolution of the glomerular filtration rate (GFR) is shown in figure 1, without difference between early and late AMR. The overall response rate to treatment (GFR maintained or returned within 25% of baseline) immediately, at 1, 6, and 12 months was 73%, 69%, 59%, and 59%, respectively. No difference in GFR for those with and without a response. There was no correlation between the inflammation score (G+ptc) with the GFR in any period. There was an inverse correlation between the chronicity score (ci+ct+cg+cv) and the GFR at diagnosis, at the end of treatment, at 1 and 12 months (-0.261, -0.261, -0.237 and -0.146, respectively).

Conclusions: There were not differences in the response to treatment between early or late AMR and should not determine the therapeutic attitude. Protocol biopsies detected more than half of AMR, demonstrating its relevance.