Objective: We aimed to investigate if sterile leukocyturia reflects increased intragraft immune activity and gene expression profiles of transplant kidney biopsies differ from patients without sterile leukocyturia.

Methods: We identified 33 biopsies with non-specific interstitial fibrosis/tubular atrophy (IFTA) for gene expression profiling comparing to 15 normal transplant kidney biopsies (Group I). Biopsies with a diagnosis of acute or chronic rejection, recurrent or de novo glomerular disease, or polyoma nephropathy were excluded. Sterile leukocyturia was defined by the presence of leukocytes in the urine (>10¯o;L) without bacterial growth in urine culture. The urinalysis and urine culture were done within 1 month before or after the biopsy. The gene expression profiles were studied by Affymetrix HuGene 1.0 ST expression arrays.

Results: Among the 33 biopsies with IFTA, 24 patients (Group 2) had no sterile leukocyturia and 9 patients (Group 3) had sterile leukocyturia. Both groups had similar demographics characteristics in terms of age, race, and sex, type of transplant, previous history of transplantation or acute rejection, donor characteristics, panel reactive antibody levels and immunosuppressive treatment. There were no differences in acute and chronic Banff injury scores. There was no statistically significant difference in gene expression profiles between the Groups 1 and 2. When Group 3 biopsies were compared to Group 1 and 2 biopsies, significantly increased gene transcripts associated with Cytotoxic T-cell (CAT), T-regulatory cell (TREG), and Constitutive Macrophage (CMAT) (Table 1), P-value for significance <0.05).

Conclusions: The biopsies of the patients with sterile leukocyturia showed increased expression of gene transcripts associated with T cells indicating an heightened intragraft immune activity. Those patients might require close monitoring of their allograft function.

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