Platelet Aggregation in the Diagnosis of Acute Graft Rejection

Platelets play a key role not only in hemostasis but also in inflammation and immune responses. Their activation, characterized by adhesion, integrin-mediated aggregation, thromboxane A₂ production, and surface expression of markers such as P-selectin, contributes to interactions with T lymphocytes and amplification of immune signaling. Emerging evidence suggests that platelet activation may participate in early mechanisms of kidney graft injury. Studies have demonstrated platelet accumulation in glomerular and peritubular capillaries during antibody-mediated rejection, likely mediated by donor-specific antibodies and endothelial activation via von Willebrand factor. Elevated platelet activation markers such as PF4 and P-selectin have also been associated with T-cell-mediated rejection. This pilot study investigates whether changes in platelet aggregation and platelet activation markers can serve as non-invasive indicators of acute kidney allograft rejection. Platelet function is measured using optical aggregometry, flow cytometry of P-selectin (CD62-P), and soluble P-selectin levels. These parameters are correlated with histological findings from protocol biopsies at 3 and 12 months post-transplant, as well as from indication biopsies performed for suspected rejection. The study includes adult kidney transplant recipients monitored longitudinally and a cohort of patients with graft dysfunction requiring indication biopsy. Concurrent assessments include renal function, donor-specific antibodies, levels of immunosupression (tacrolimus), metabolic parameters, and imaging. By comparing platelet activation profiles with biopsy-proven rejection, the study aims to determine whether platelet-based biomarkers can support early, non-invasive detection of cellular or antibody-mediated allograft injury and complement traditional biopsy-based diagnostics.