Urinary C‑X‑C motif chemokine 13 is a noninvasive biomarker of antibody‑mediated renal allograft rejection.

Noninvasive monitoring methods of immune status are preferred by transplant recipients. The present study investigated whether urinary C‑X‑C motif chemokine 13 (CXCL13) had the potential to reflect ongoing immune processes within renal allografts. Using an ELISA assay, the level of urinary CXCL13 was quantified in a total of 146 renal allograft recipients and 40 healthy controls at scheduled intervals and at the time of the indicated or protocol biopsy. The results of the present study revealed that urinary CXCL13/creatinine (Cr) was lower in normal transplants compared with in those with acute tubular necrosis (ATN; P=0.001), chronic allograft nephropathy (CAN; P=0.01), and acute rejection (AR; P<0.0001), which was associated with a good diagnostic performance for AR [area under the curve (AUC)=0.818, P<0.0001). In addition, urinary CXCL13/Cr levels in patients with AR were also higher than that of patients with graft dysfunction but no rejection, including ATN and CAN (P=0.034). Notably, urinary CXCL13 distinguished between acute antibody‑mediated rejection (ABMR) and acute cellular rejection, with an AUC of 0.856. Furthermore, patients with steroid‑resistant AR exhibited significantly increased urinary CXCL13/Cr levels than patients with reversible AR (P=0.001). Additionally, elevated levels of urinary CXCL13/Cr within the first month of transplant were predictive of graft function at 3 and 6 months (P=0.044 and P=0.04, respectively). Collectively, the findings of the present study indicated that the noninvasive investigation of urinary CXCL13/Cr may be valuable for the detection of AR, particularly ABMR. In addition, high urinary CXCL13/Cr levels predicted a poor response to steroid treatment and compromised graft function.