SRS310 - Kidney perfusate as a non-invasive source for tissue-resident T cell profiling

Abstract The kidney harbours a diverse immune repertoire, including populations of tissue-resident lymphocytes that play critical roles in local immune surveillance, antiviral defence and allograft outcomes. However, a detailed study of these cells is limited by the invasive nature of tissue biopsy. Kidney perfusates, collected during a live-donor nephrectomy, offer a unique and minimally invasive ‘liquid biopsy’ that may capture these resident immune populations in healthy donors at the time of transplantation. In this study, we compared lymphocyte subsets obtained from kidney perfusates with paired peripheral blood mononuclear cells (PBMCs) from the same donors (n = 17) to determine whether perfusate samples can be used as a tractable alternative to allow the characterisation of tissue-resident T cells and investigate the expression of activation, inhibitory and exhaustion-related phenotypic markers. Multiparametric spectral flow cytometry revealed that perfusate-derived lymphocytes exhibiting phenotypic features characteristic of residency, including enrichment for CD69⁺ and CXCR6⁺ CD8⁺ T cells, as well as tissue-adapted CD4⁺ subsets, could be identified by this approach. Importantly, these populations were distinct from paired circulating PBMCs, which predominantly displayed central and effector memory profiles with minimal residency markers. These preliminary findings support the concept that the kidney perfusate can serve as a tractable and scalable proxy for studying the phenotype and function of resident immune cells without the need for invasive biopsy. This approach provides a window into an organ’s immune microenvironment at the time of transplantation, with potential applications in biomarker discovery, risk stratification for viral reactivation and rejection, and ultimately improved transplant outcomes.