Prevalence of Angiotensin II Type I Receptors (AT1R) Antibodies (Ab) in Kidney Allograft Recipients.

Abstract

Concurrent development of DSA and AT1R Ab is associated with increased risk of kidney graft loss. HLA Ab is routinely measured in kidney recipients pre- and post-transplant (Tx) but not AT1R Ab. There is a paucity of data concerning accepted cutoff for AT1R Ab positivity. The prevalence of AT1R Ab in the transplant population is not clearly defined. Monitoring of AT1R Ab and donor specific antibodies (DSA) may effect patient management. Aim: The prevalence of AT1R antibodies in renal transplant recipients is not consistent in published reports. The aim of this study was to determine the prevalence of AT1R antibodies in kidney recipients. Methods: 56 recipients were tested for DSA and AT1R Ab prior and 6-12 months post Tx. Flow cytometry screening beads and class I/II single antigen bead assays were used with a positive cutoff of 1000 MFI. AT1R Abs were determined using commercially available ELISA (One Lambda). A cutoff of 17 U/mL was used to determine positivity based on package insert. A cutoff of 15 U/mL was also assessed based on published data. Results: Pre-transplant, 9 of 56 (16%) kidney Tx recipients had AT1R Ab based on a cutoff of 17 U/mL. The cutoff of 15 U/mL identified an additional 9 AT1R positive patients. Seven of the 18 AT1R positive patients also had Class I and/or II HLA Ab pre-Tx, but only 1 patient had HLA DSA. Two of 18 AT1R positive patients developed de novo DSA 6 - 12 months post-Tx. 1 of 2 patients with de novo DSA patients remained positive for AT1R antibodies 6 - 12 months post-Tx. 1 patient had evidence of Ab mediated rejection (AMR) with negative C4d immunofluorescence. Conclusion: AT1R Ab can be detected pre and post Tx in kidney recipients. More work is needed to establish cutoff for AT1R test and correlation with short and long term outcomes. AT1R presence may be supportive in detecting AMR in C4d negative cases.