Donor-recipient HLA molecular mismatch and T follicular helper-related genetic variants are associated with dnDSA development after kidney transplantation.

INTRODUCTION: De novo donor-specific HLA antibodies (dnDSAs) after kidney transplantation arise through coordinated antigen recognition, T-cell-dependent B-cell activation, and subsequent germinal center reactions. Donor-recipient HLA molecular mismatch reflects donor-derived antigenic disparity and is associated with dnDSA development; however, it does not fully explain interindividual variability in humoral alloimmune responses. We hypothesized that integrating HLA molecular mismatch with recipient T follicular helper (Tfh) cell-related immunogenetic variation would improve risk stratification and provide additional insight into variability in alloantibody responses.

METHODS: In this retrospective single-center cohort study, we analyzed 210 kidney transplant recipients who underwent transplantation between 2011 and 2024. Donor-recipient HLA molecular mismatch loads were quantified using eplet mismatch analysis, Predicted Indirectly ReCognizable HLA Epitopes-T cell (PIRCHE-T2), and HLA Epitope Mismatch Algorithm (HLA-EMMA). Recipient single-nucleotide polymorphisms in Tfh-related genes (CXCR5 rs3922 and CTLA4 rs231775) were genotyped. The primary endpoint was class II dnDSA development, defined as newly detected donor-specific antibodies with a normalized mean fluorescence intensity >1, 000 and persistence confirmed at least six months later. Associations between candidate variables and class II dnDSA development were assessed using Firth penalized logistic regression.

RESULTS: During follow-up, 20 recipients (9.5%) developed class II dnDSAs. Higher class II molecular mismatch loads were significantly associated with dnDSA development, with HLA-EMMA showing the strongest association among the evaluated metrics. In multivariable analysis, high HLA-EMMA class II load and Tfh cell-related immunogenetic variation were independently associated with class II dnDSA development. Recipients with both high HLA-EMMA class II load and Tfh-related polymorphisms showed the highest cumulative incidence of dnDSA development.

CONCLUSION: These findings suggest that donor-derived structural antigenicity and recipient Tfh-related immunogenetic variation are associated with the development of class II dnDSAs after kidney transplantation. The identified thresholds and integrated risk stratification approach are exploratory and require validation in independent cohorts before clinical application of the model.