Systemic Inflammatory Profiles Associated with Chronic Antibody-Mediated Rejection: A 200-Patient Study Using OLINK Explore Proteomics

Background: Chronic antibody-mediated rejection (cAMR) is a major cause of late kidney allograft failure. We aimed to characterize systemic inflammatory proteomic profiles associated with biopsy-proven cAMR using high-throughput multiplex analysis. Methods: In this single-center case-control study, we analyzed serum from 200 adult kidney transplant recipients: 100 with biopsy-confirmed cAMR and 100 stable matched controls without evidence of rejection. Proteomic profiling was performed using the OLINK Explore Inflammation Panels 1 and 2, targeting 735 inflammatory proteins. After quality control and detection filtering (limit of detection >0.5 in >75% of samples), 671 unique proteins were retained for analysis. Differential expression was assessed using linear modelling with empirical Bayes moderation (limma) with adjustment for confounding variables, and correction for multiple testing using the False Discovery Rate method. Results: Sixty proteins were differentially expressed between cAMR and control groups (adjusted p<0.05), with 14 proteins surpassing the adjusted p<0.01 threshold. Top upregulated proteins in cAMR included CXCL9 (fold change 1.73, adj. p = 0.0026), KRT19 (fold change 1.64, adj. p = 0.0026), CSF1 (fold change 1.26, adj. p = 0.0026), and CCL23 (fold change 1.30, adj. p = 0.0026). Fold changes across differentially expressed proteins ranged from 1.19 to 1.73. Functional annotation revealed enrichment in pathways related to T-cell and monocyte recruitment, macrophage activation, extracellular matrix remodelling, and immune regulation. Proteins were categorized into biological processes including immune activation (n=20), tissue remodelling/fibrosis (n=12), leukocyte adhesion/migration (n=8), and metabolic regulation (n=5). Conclusion: This study represents one of the largest proteomic analyses of cAMR to date, utilizing a 735- inflammatory protein panel. We identified distinct circulating signatures of immune activation and tissue injury in cAMR patients, highlighting potential biomarker candidates for non-invasive monitoring and therapeutic targeting. These findings contribute to the growing evidence base supporting the development of precision diagnostics in kidney transplantation and warrant further validation in multicenter cohorts.