Kidney Week

Abstract: TH-PO0895

Urine Immune Cells May Be a Sensitive Mechanistic Biomarker for Subclinical Allograft Rejection

Session Information

• Transplantation: Basic Research
  November 06, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Transplantation

• 2101 Transplantation: Basic

Authors

• Heng, Jun Wei, National University of Singapore, Singapore, Singapore

Jun Wei Heng, MMSc

• Quek, Li Ling, Khoo Teck Puat - National University Children's Medical Institute, Singapore, Singapore

Li Ling Quek, MBBS

• Chan, Chang-Yien, National University of Singapore, Singapore, Singapore

Chang-Yien Chan, PhD

• Teo, Sharon, Khoo Teck Puat - National University Children's Medical Institute, Singapore, Singapore

Sharon Teo, MBBS

• Lau, Yew Weng Perry, National University of Singapore, Singapore, Singapore

Yew Weng Perry Lau, MBBS

• Ng, Kar Hui, National University of Singapore, Singapore, Singapore

Kar Hui Ng, MBBS

• Yap, Hui Kim, National University of Singapore, Singapore, Singapore

Hui Kim Yap, MD, FASN

• Lu, Liangjian, Khoo Teck Puat - National University Children's Medical Institute, Singapore, Singapore

Liangjian Lu, MA, MBChB

Background

Donor-specific antibodies (DSA) and donor-derived cell-free DNA (cfDNA) are non-invasive biomarkers currently used to monitor allograft rejection. However, only ~50% of DSA⁺ patients have ongoing allograft rejection, and cfDNA can be elevated by non-immune causes such as infection or ischaemia. This study aims to evaluate whether urine immune cell monitoring can detect early signs of allograft rejection in a paediatric kidney transplant cohort.

Methods

14 patients (age: 18.2±1.9 years; 35.7% male) undergoing clinical DSA and cfDNA monitoring were recruited and assigned to 4 groups based on DSA/cfDNA status: G1 (DSA⁺cfDNA⁺, n=2; samples concurrent with biopsy-proven acute rejection), G2 (DSA⁺cfDNA^-, n=3), G3 (DSA^-cfDNA⁺, n=4), and G4 (DSA^-cfDNA^-, n=5). Urinary immune cells were quantified by flow cytometry (markers: CD45, CD3, CD4, CD8, CD14, CD19, CCR7, CD45RA, CD45RO, CD25). Absolute counts (cells/mL) were derived using flow-count fluorospheres (Beckman Coulter) and normalised to urine volume. Group comparisons were performed using t-tests.

Results

Compared to G4, G1 patients showed (i) increased CD8⁺CCR7^-CD45RO^- TEMRA cells (42.96±16.20 vs 5.32±10.1 cells/ml; p=0.012) and reduced naïve:memory CD8⁺ ratio (0.019±0.004 vs 0.251±0.122; p=0.013), (ii) elevated CD4⁺ T cells (97.96±17.47 vs 20.42±38.55; p=0.047) and CD4⁺CCR7^-CD45RO⁺ effector memory T cells (66.38±5.58 vs 11.14±22.13; p=0.021), and (iii) higher CD3^-CD56⁺ NK cells (32.64±9.13 vs 1.79±2.80; p<0.001). These findings reflect a cognate memory response against the allograft, in line with biopsy-proven rejection. Early changes were also seen in G2 and G3 patients who may have subclinical allograft inflammation. DSA⁺cfDNA^- G2 patients showed a similar reduction in naïve:memory CD8⁺ ratio compared to G4 (0.085±0.014 vs 0.251±0.122; p=0.038). DSA^-cfDNA⁺ G3 patients had elevated CD8⁺CCR7⁺CD45RO⁺ central memory cells (5.48±2.37 vs 1.25±1.36; p=0.012) compared to G4, which may represent an early event preceding the effector memory predominance seen in G1.

Conclusion

Urinary immune cells may be a sensitive mechanistic biomarker of intragraft immune activation. Used alongside established biomarkers like DSA and cfDNA, they could improve detection of subclinical allograft injury, and thus guide biopsy decisions and immunosuppression adjustment.

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025wpk7s4vb