Introduction: Antibody mediated rejection (ABMR) is now recognized as responsible for the loss of most kidney grafts. The presence of donor specific antibodies (DSA) in the recipient’s serum either pre transplant (preDSA) or develop after transplantation (de novo DSA) is the main risk factor for ABMR both clinical and subclinical. On the other hand clinical and sub clinical T cell mediated rejection (TCMR) is associated with the development of de novo DSA. In this context graft histology and immunologic monitoring for the presence of DSA after transplantation are considered valuables tools to guide therapeutic decisions.
Objective: Our purpose was to describe the findings of the histologic and immunologic monitoring after renal transplantation at CEMIC.
Materials and Methods: This was a Retrospective cohort analysis of all patients who received a renal transplant at CEMIC from 01/01/2012 to 31/12/2016. Patients who presented technical failure were excluded.
DSA Monitoring: panel reactive antibodies (PRA) by ELISA were tested pre transplant and then at 6 months, 1, 3, 5 and 10 years post-transplant. In cases where PRA>0, history of previous transplants, transfusions, pregnancy or known DSA, a single antigen bead (SAB) Luminex essay (OneLambda®) was also performed.
Histologic monitoring: surveillance percutaneous renal graft biopsy (PRB) was performed at 6 months,1, 3, 5 and 10 years post-transplant. PRB for cause was also indicated whenever there were graft dysfunction or immunosuppression changes.
Patients with PreDSA were desensitized and acute rejections were treated  accordingly per local practice guidelines.
Results: During the analyzed period 179 renal transplants were performed at CEMIC. 8 cases of technical failure were excluded, leaving 171 patients for analysis. Median age was 54,5±15 years, 69,6% were males, 73,7% received kidneys from diseased donors. 22(12,8%) patients had a positive PRA pre transplant (ELISA) and 32(18,7%) had anti HLA antibodies by SAB, 14/32 were DSA. Median follow up time was 43, 7±20 months. During this period all patients with preDSA showed a reduction in MFI levels. 7/171 (4%) developed de novo DSA post-transplant. Additionally 13/171 (7,6%) developed anti HLA antibodies without DSA detected.
A total of 293 PRB were performed of which 168/293 (57,3%) were surveillance biopsies accomplished during the first year. Acute rejection was diagnosed in 67/293(22, 8%), 14/67 (20,9%) were borderline changes, 45/67 (67,1%) were TCMR and 8/67 (11,9%) were ABMR or mixed rejection. 24/67 (35,8 %) were subclinical rejections diagnosed in surveillance biopsies.
8/21(38%) of patients with DSA developed ABMR or mixed rejection, 3/21(14,2%) lost their graft and 2/21(9,5%) died. Death censored graft survival at 2 years was 82,9% vs 95,2% in DSA vs non DSA patients (NS)
Conclusions: In our experience, DSA and histologic post-transplant monitoring were useful tools for the detection of aloimmune events in general and those subclinical in particular.