Gewebsständige Lymphozyten in der humanen Niere: Eigenschaften, Spezifität und ihre Bedeutung für die Nierentransplantation und den Nierenkrebs

Tissue-resident memory (TRM) lymphocytes are attracting increasing attention. Identification of TRM cells in various tissues, such as skin, lung, intestine, brain or liver, suggest that they play a role in local pathogen detection and that they mediate a first line defense within the tissue. So far, no detailed investigation of the specificity and function of TRM cells within the human kidney exists, as well as data related to their role in kidney transplantation and kidney cancer. In this study, isolated lymphocytes out of blood, human peri-tumor and tumor kidney tissue were analyzed using flow cytometry and MELC histology. Using these technologies, the existence of the major T cell TRM subsets characterized by CD8+ CD69+CD103+ and CD8+ CD69+CD103- expression was demonstrated within the human kidney. These CD8+ TRM T cells displayed an activated phenotype and a pro-inflammatory effector profile, exhibiting increased IL-17 production. Interestingly, increased frequencies of CD8+ TRM T cells were associated with increased age and, moreover, a correlation of CD4+ and CD8+ TRM cell frequency with eGFR could be detected. Beside the presence of TRM T cells, renal CD56dim and CD56bright NK cells and mucosa-associated invariant T (MAIT) cells expressing the TRM markers CD69 and CD103 were identified. Furthermore, tumor-derived CD8+ TRM cells were identified to upregulate the exhaustion markers PD-1 and TOX and were functionally impaired in metastasized patients. Finally, CD8+ T cells specific for BKV, CMV, EBV and influenza could be detected within renal peri-tumor and tumor tissue. Interestingly, these cells did not display a TRM phenotype. In summary, these data present a detailed overview of the phenotype and function of human renal TRM cells for the very first time, giving indications for their potential relevance in kidney transplantation and cancer.Gewebsständige Lymphozyten (engl.: tissue resident memory (TRM) lymphocytes) stehen derzeit im Fokus der Forschung. Bislang wurden diese in verschiedenen Geweben identifiziert, darunter beispielsweise in Haut, Lunge, Darm, Gehirn und Leber. Ihre Haupteigenschaft besteht in der schnellen und lokalen Abwehr von Pathogenen und dem Schutz vor Reinfektion des jeweiligen Organs. Bislang wurden gewebsständige Lymphozyten in der humanen Niere zwar identifiziert, diese jedoch nicht hinsichtlich ihrer Spezifität und Funktion, sowie ihrer Rolle für die Nierentransplantation und Nierentumore analysiert. Ziel dieser Studie war es, Lymphozyten, welche aus Blut, peri-Tumor und Tumorgewebe der humanen Niere isoliert wurden, mittels Durchflusszytometrie und MELC Histologie zu analysieren. Dabei konnten TRM T Zell Hauptpopulationen in der humanen Niere identifiziert werden, welche durch die Expression der Marker CD8+ CD69+CD103+ und CD8+ CD69+CD103- gekennzeichnet waren. Diese CD8+ TRM T Zellen zeigten einen aktivierten Phänotyp und ein pro-inflammatorisches Effektorprofil mit gesteigerter Produktion von IL-17. Interessanterweise konnte eine erhöhte Frequenz von CD8+ TRM T Zellen mit ansteigendem Alter assoziiert werden. Außerdem konnte gezeigt werden, dass die Frequenz von CD8+ und CD4+ TRM T Zellen mit der glomerulären Filtrationsrate (eGFR) korrelierte. Neben T Zellen konnten außerdem auch CD56dim und CD56brigh NK Zellen, sowie, Mukosa-assoziierte invariante T (MAIT) Zellen identifiziert werden, welche die TRM Marker CD69 und CD103 exprimierten. CD8+ TRM T Zellen aus dem Tumor waren zudem durch eine gesteigerte Expression der Marker PD-1 und TOX gekennzeichnet und zeigten in metastasierten Patienten eine geschwächte Funktionalität. Schließlich wurden CD8+ T Zellen, welche spezifisch für BKV, CMV, EBV sowie das Influenza Virus waren, im renalen peri-Tumor und Tumorgewebe identifiziert, welche jedoch keinen TRM Phänotyp zeigten. Somit gibt diese Studie einen detaillierten Überblick über den Phänotyp und die Funktion von TRM Zellen in der humanen Niere, sowie einen Hinweis darauf, welchen Einfluss sie auf die Nierentransplantation und Nierentumore haben könnten

Mucosal associated invariant T cells are differentially impaired in tolerant and immunosuppressed liver transplant recipients

Mucosal associated invariant T (MAIT-) cells represent a semi-invariant T cell population responsive to microbial vitamin B metabolite and innate cytokine stimulation, executing border tissue protection and particularly contributing to human liver immunity. The impact of immunosuppressants on MAIT cell biology alone and in context with solid organ transplantation has not been thoroughly examined. Here, we demonstrate that in vitro cytokine activation of peripheral MAIT cells from healthy individuals was impaired by glucocorticoids, whereas antigen-specific stimulation was additionally sensitive to calcineurin inhibitors. In liver transplant (LTx) recipients, significant depletion of peripheral MAIT cells was observed that was largely independent of the type and dosage of immunosuppression, equally applied to tolerant patients, and was reproducible in kidney transplant recipients. However, MAIT cells from tolerant LTx patients exhibited a markedly diminished ex vivo activation signature, associated with individual regain of functional competence toward antigenic and cytokine stimulation. Still, MAIT cells from tolerant and treated liver recipients exhibited high levels of PD1, accompanied by functional impairment particularly toward bacterial stimulation that also affected polyfunctionality. Our data suggest interlinked effects of primary liver pathology and immunosuppressive treatment on overall MAIT cell fitness after transplantation and propose their monitoring in context with tolerance induction protocols

Comparison of Three Cellular Assays to Predict the Course of CMV Infection in Liver Transplant Recipients

To estimate protection from cytomegalovirus (CMV) replication after solid organ transplantation, CMV serology has been considered insufficient and thus CMV immunity is increasingly assessed by cellular in vitro methods. We compared two commercially available IFN-γ ELISpot assays (T-Track CMV and T-SPOT.CMV) and an IFN-γ ELISA (QuantiFERON-CMV). Currently, there is no study comparing these three assays. The assays were performed in 56 liver transplant recipients at the end of antiviral prophylaxis and one month thereafter. In CMV high- or intermediate-risk patients the two ELISpot assays showed significant correlation (p < 0.0001, r > 0.6) but the correlation of the ELISpot assays with QuantiFERON-CMV was weaker. Results of both ELISpot assays were similarly predictive of protection from CMV-DNAemia ≥500 copies/mL [CMV pp65 T-SPOT.CMV at the end of prophylaxis: area under curve (AUC) = 0.744, cut-off 142 spot forming units (SFU), sensitivity set to 100%, specificity 46%; CMV IE-1 T-Track CMV at month 1: AUC = 0.762, cut-off 3.5 SFU, sensitivity set to 100%, specificity 59%]. The QuantiFERON-CMV assay was inferior, reaching a specificity of 23% when setting the sensitivity to 100%. In conclusion, both CMV-specific ELISpot assays appear suitable to assess protection from CMV infection/reactivation in liver transplant recipients

The Cytomegalovirus-Specific IL-21 ELISpot Correlates with Allograft Function of Kidney Transplant Recipients

In kidney transplant recipients, the cytomegalovirus (CMV) is frequently causing infection/reactivation and can trigger allograft rejection. To assess the risk of reactivation, the cellular immune response against CMV is increasingly assessed by cellular in vitro methods, such as the interferon (IFN)-γ ELISpot. In the current study we compared the IFN-γ ELISpot with our newly established CMV-specific ELISpot assays determining IL-17A, IL-21, IL-22, granzyme B, and perforin and correlated the results with flow cytometric data and clinical parameters. In 77 kidney transplant recipients, the highest frequency was observed for CMV pp65-specific cells secreting IFN-γ, followed by cells secreting IL-21 (62.9 and 23.2 Δ spot forming cells/105 cells). We observed a positive correlation between the percentage of CMV-specific CD3+ CD4+ CD154+ cells and results of the CMV-specific IL-21 ELISpot (p = 0.002). Results of the CMV pp65-specific IL-21 ELISpot correlated negatively with kidney function (estimated glomerular filtration rate, p = 0.006) and were significantly higher in women (p = 0.005). IL-21, a cytokine involved in aging that is secreted by activated CD4+ T cells, may also impact on allograft function. Thus, the CMV-specific IL-21 ELISpot could become a new tool to assess if CMV seropositivity represents a hazard for the graft