Functional activity of anti-endothelin type A receptor antibodies as a predictive tool of allograft injury in pediatric kidney transplantation

Abstract

Background Antibody-mediated rejection remains the leading cause of kidney allograft failure in pediatric recipients. While non-HLA antibodies targeting G protein-coupled receptors, particularly anti-endothelin-1 type A receptor (ETAR) antibodies, have been implicated in allograft injury, their functional activity and independent pathogenic role in pediatric kidney transplantation remain poorly characterized. Methods In this study involving 46 pediatric kidney transplant recipients, anti-ETAR antibodies were quantified and their functional activity assessed using a β-arrestin–based luminometric bioassay in ETAR-transfected CHO cells. Furthermore, IgG-induced migration of T-lymphocytes and NK-92 cells was evaluated by chemotaxis assay. Renal function was monitored longitudinally. Predictive models of eGFR decline between consecutive follow-up visits were developed using restricted cubic spline regression with bootstrap validation. Results Patient-derived IgG exhibited concentration-dependent agonistic activity on ETAR, including samples with anti-ETAR IgG below the standard positivity threshold (17 U/mL). Moreover, IgG enhanced endothelin-1–induced receptor activation, independently of anti-ETAR antibody levels. IgG from pediatric transplant recipients with elevated anti-ETAR levels significantly increased T-lymphocyte and NK-92 cell migration, irrespective of the presence of anti-HLA antibodies. Anti-ETAR IgG levels were associated with immune cell migration and with the decline in eGFR (Spearman ρ = 0.52). In multivariable modeling, however, antibody concentration retained no validated predictive information after bootstrap optimism correction, whereas IgG-induced T-cell migration remained associated with eGFR decline after adjustment for time since transplantation and for HLA donor-specific antibodies (DSA). Conclusion In pediatric kidney transplant recipients, anti-ETAR antibodies are functionally active irrespective of their levels, promoting receptor signaling and immune cell recruitment associated with graft function deterioration. These results suggest that functional assessment, particularly T-cell migration, may provide complementary information beyond antibody concentration and warrants further investigation as a potential approach to risk stratification.

The authors' abstract, as published at the source. Frontiers in Immunology, 2026 · DOI ↗