Background: Donor-specific antibodies (DSA) are measured at the time of transplantation to predict renal allograft outcome, but pretransplantation DSA are sometimes not adequate to predict antibody-mediated rejection (AMR). We previously developed a flow cytometric assay that could measure the number of antibody-secreting cells (ASCs) instead of DSA. Here, we evaluated the performance of the flow cytometric ASC assay in predicting renal allograft rejection and compared it with that of the enzyme-linked immunospot (ELISpot) assay.
Methods: We enrolled 25 patients who received renal transplantation between May 2017 and August 2017 at Seoul National University Hospital. Mononuclear cells separated from patient peripheral blood obtained on pretransplantation day 1 were incubated with CpG 2006, human CD40L, interleukin-21, and donor or autologous lymphocyte lysates for 6 days. Flow cytometry and ELISpot assay (Mabtech) were performed to measure the ASCs and their association with graft rejection.
Results: The number of donor-reactive ASCs, as measured by flow cytometry, was higher in the rejection group than in the nonrejection group (mean ± standard deviation [SD], 3688.9 ± 3875.3 vs 257.9 ± 297.3, P = .014), and no significant difference was observed in the ELISpot assay. Multiple linear regression analysis showed that the number of donor-reactive ASCs measured by flow cytometry was independently and negatively associated with the number of rejection-free days (P = .008, partial R2 = 0.368, adjusted R2 = 0.496).
Conclusion: After renal transplantation, an increased number of donor-reactive ASCs, as measured by flow cytometry, was associated with allograft rejection. This may be useful to predict renal allograft rejection by measuring the sensitization status of patients who are awaiting renal transplantation.
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