*Purpose: Eplet mismatches are associated with development of de novo DSA (dnDSA) in kidney transplant recipients. However, it remains unclear how the degree of eplet mismatch correlates with antibody mediated rejection (ABMR) or allograft loss among patients with known dnDSA. We aimed to 1) determine correlation between eplet mismatch and ABMR and allograft loss 2) determine mean time to ABMR and allograft loss following dnDSA detection.

*Methods: We performed a retrospective observational study of kidney transplant recipients (n=967) transplanted between 10/2007-5/2014, who developed persistent dnDSA (n=44). High resolution typing was inferred from low to medium resolution HLA typing based on the individual’s ethnicity and NMDP haplotypes. Based on donor and recipient typing after subtracting for the shared eplets, the eplet mismatch score was calculated using the Epvix algorithm (accessed at www.epvix.br) for confirmed and exposed eplets. 450 protocol and for-cause biopsies among 95.3% (42/44) studied patients were reviewed.

*Results: The mean (SD) and median (IQR) eplet mismatch was 69.8(22.8) and 68(56-81.5). Following dnDSA detection, the incidence of ABMR was 71.4% (30/42) and 5 year death censored allograft survival was 67.4% during the mean (SD) follow-up time of 5.3 (3.1) years. Eplet mismatch was not correlated with either ABMR (Figure 1) or death-censored allograft survival. Factors associated with reduced incidence of ABMR included: medication adherence and dnDSA with an MFI<3000 at detection. The incidence of ABMR was only 35.7% (15/42) among adherent patients with DSA MFI<3000.

*Conclusions: Eplet mismatch was not correlated with ABMR or graft loss among kidney transplant patients with known dnDSA. Features associated with a reduced incidence of ABMR included medication adherence and dnDSA MFI<3000 at presentation.

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