Immune monitoring of kidney allograft recipients and personalized therapeutics may help reach the aspirational goal of "one transplant for life." The invasive kidney biopsy procedure, the diagnostic tool of choice, has become safer and the biopsy classification more refined. Nevertheless, biopsy-associated complications, interobserver variability in biopsy specimen scoring, and costs continue to be significant concerns. The dynamics of the immune repertoire make frequent assessments of allograft status necessary, but repeat biopsies of the kidney are neither practical nor safe. To address the existing challenges, we developed urinary cell mRNA profiling and investigated the diagnostic, prognostic, and predictive accuracy of absolute levels of a hypothesis-based panel of mRNAs encoding immunoregulatory proteins. Enabled by our refinements of the PCR assay and by investigating mechanistic hypotheses, our single-center studies identified urinary cell mRNAs associated with T cell–mediated rejection, antibody-mediated rejection, interstitial fibrosis and tubular atrophy, and BK virus nephropathy. In the multicenter National Institutes of Health Clinical Trials in Organ Transplantation-04, we discovered and validated a urinary cell three-gene signature of T-cell CD3 chain mRNA, interferon gamma inducible protein 10 (IP-10) mRNA, and 18s ribosomal RNA that is diagnostic of subclinical acute cellular rejection and acute cellular rejection and prognostic of acute cellular rejection and graft function. The trajectory of the signature score remained flat and below the diagnostic threshold for acute cellular rejection in the patients with no rejection biopsy specimens, whereas a sharp rise was observed during the weeks before the biopsy specimen that showed acute cellular rejection. Our RNA sequencing and bioinformatics identified kidney allograft biopsy specimen gene signatures of acute rejection to be enriched in urinary cells matched to acute rejection biopsy specimens. The urinary cellular landscape was more diverse and more enriched for immune cell types compared with kidney allograft biopsy specimens. Urinary cell mRNA profile–guided clinical trials are needed to evaluate their value compared with current standard of care.

肾脏同种异体移植受者的免疫监测和个性化治疗可能有助于实现“终生一次移植”的理想目标。作为首选诊断工具的侵入性肾活检程序已变得更加安全，活检分类也更加精细。然而，活检相关的并发症、活检标本评分的观察者间差异以及成本仍然是重要的问题。免疫组库的动态变化需要经常评估同种异体移植物的状态，但重复进行肾脏活检既不实用也不安全。为了解决现有的挑战，我们开发了尿细胞 mRNA 分析，并研究了一组基于假设的编码免疫调节蛋白的 mRNA 的绝对水平的诊断、预后和预测准确性。通过我们对 PCR 测定的改进和通过研究机制假设，我们的单中心研究确定了与 T 细胞介导的排斥反应、抗体介导的排斥反应、间质纤维化和肾小管萎缩以及 BK 病毒肾病相关的尿细胞 mRNA。在多中心美国国立卫生研究院器官移植临床试验 04 中，我们发现并验证了 T 细胞 CD3 的尿细胞三基因特征链 mRNA、干扰素γ诱导蛋白 10 (IP-10) mRNA 和 18s 核糖体 RNA，可诊断亚临床急性细胞排斥反应和急性细胞排斥反应，并可预测急性细胞排斥反应和移植物功能。在没有排斥活检标本的患者中，签名评分的轨迹保持平坦且低于急性细胞排斥的诊断阈值，而在显示急性细胞排斥的活检标本之前的几周内观察到急剧上升。我们的 RNA 测序和生物信息学确定了急性排斥反应的肾脏同种异体移植活检标本基因特征在与急性排斥反应活检标本相匹配的尿细胞中富集。与肾同种异体移植活检标本相比，尿液细胞景观更多样化，免疫细胞类型更丰富。