Non-Invasive Detection of Acute Kidney Allograft Rejection Using [18F]FB-IL2 PET-CT: A First in Human Proof-of-Concept Study

Despite its life-saving role, kidney transplantation is frequently complicated by acute T-cell–mediated rejection (TCMR), currently only diagnosed invasively by biopsy. [¹⁸F]FB-IL2 PET-CT is a novel molecular imaging approach that binds activated T cells via the IL-2 receptor. In this proof-of-concept study, 11 kidney transplant recipients with suspected rejection underwent [¹⁸F]FB-IL2 PET-CT. Tracer uptake in cortex versus medulla was quantified and compared with biopsy results, kidney function and peripheral blood T cells. Four patients were diagnosed with biopsy-confirmed TCMR. The cortex-to-medulla distribution volume ratio distinguished TCMR from non-rejection (p = 0.02) and correlated with interstitial inflammation (r = 0.68, p = 0.04) and proteinuria (r = 0.60, p = 0.05). No tracer administration adverse events were observed. [¹⁸F]FB-IL2 PET-CT appears safe and may provide a non-invasive alternative to biopsy for detection of acute TCMR in kidney transplant recipients. Larger, prospective studies are warranted to confirm its clinical utility.