We are focusing on the molecular and cellular mechanisms that determine the function of CD8 T cells within liver tissue. Such regulation of T cell function in the liver occurs in the context of the unique liver microenvironment, where T cells reaching the liver with the bloodstream interact with liver sinusoidal cell populations. In the past, we have identified that liver tissue cells, such as liver sinusoidal endothelial cells, are endowed with functional properties of immune cells that include scavenging of antigens from the circulation and antigen (cross)presentation of endocytosed antigens to CD8 T cells, which leads to the generation of dysfunctional T cells. We have further identified that the accumulation of inflammatory monocytes in the liver during acute local inflammation educates T cells for clearance of persistent Hepatitis B Virus (HBV) infection. In contrast, continuous TNF or type I Interferon signaling during chronic inflammation is associated with the loss of CD4 T cell support of CD8 T cell immunity or increased expression of IL-10 by myeloid cells to limit CD8 T cell function respectively.
More recently, we have turned our attention to characterizing the impact of metabolites on regulating immune cell functions in tissues. We discovered that transcriptional programming by IL-15 during chronic inflammation in tissues allows CD8 T cells to acquire the capacity to sense danger signals from the environment, such as extracellular ATP. This metabolite-induced activation of CD8 T cells without T cell receptor signaling leads to antigen-independent killing of neighboring cells, which we termed auto-aggressive killing. Auto-aggressive CD8 T cells mediate immune pathology in diseases characterized by sterile inflammation like non-alcoholic steatohepatitis and drive the development of cancer cells in diseased liver tissue.
During the SARS-CoV-2 pandemic, we took advantage of the unique possibility of studying human virus-specific immunity. We reported the importance of hybrid immunity resulting from vaccination and infection against SARS-CoV-2 proteins for protection from the development of COVID-19 by studying virus-specific T cell responses and the quality of virus-specific antibodies in infected individuals.
Currently, we are pursuing several lines of investigation to characterize tissue-specific regulation of immune responses and how we can exploit mechanistic insights into such immune regulation for translation into the clinics.
Local regulation of T cell immunity in the liver
During viral liver infection, virus-specific T cells can recognize their cognate antigen on MHC class I molecules on infected hepatocytes or cells cross-presenting endocytosed viral antigens released from infected hepatocytes. Due to the unique microanatomy of the liver, where T cells have to reach through endothelial fenestrae to gain access to infected hepatocytes, LSECs engage in close interaction with effector CD8 T cells. We are studying the molecular mechanisms of how LSECs regulate the function of these T cells that engage in close physical contact. Since the loss of function in virus-specific CD8 T cells, for instance, in chronic viral hepatitis, is responsible for the failure of anti-viral immunity to control infection of hepatocytes, we focus our attention on understanding the mechanistic underpinnings of this local regulation of effector T cell function by LSECs. We further evaluate the contribution of other cell populations within the liver microenvironment to this local regulation of effector CD8 T cell function.
Moreover, we further exploit the role of auto-aggressive CD8 T cells in controlling viral infection in the liver. Since auto-aggressive CD8 T cell killing does not require cognate TCR-MHC interaction, we characterize the crosstalk between conventional and auto-aggressive CD8 T cells in eliminating virus-infected hepatocytes. Together, these projects aim at achieving immune control of liver infection even when immune cell dysfunction as a hallmark of chronic infection has already developed.
Overcoming HBV-specific immune tolerance during chronic viral hepatitis by therapeutic vaccination
During chronic hepatitis B, HBV-specific CD8 T cells detected in patients are dysfunctional and scarce. So far, attempts have failed to reconstitute HBV-specific immunity and to control HBV infection in hepatocytes to terminate chronic infection and tissue damage leading to liver cirrhosis and liver cancer. A recently developed heterologous prime-boost therapeutic vaccination approach (TherVacB), developed by the research group of Prof. Ulrike Protzer at the Institute of Virology TUM has demonstrated superior efficacy in overcoming HBV-specific immune tolerance. In the context of an international EU-funded consortium, we are characterizing the HBV-specific immune responses after TherVacB therapeutic vaccination in phase Ib/IIa clinical studies.
Deciphering the crosstalk of liver tissue cells and immune cells using imaging mass spectrometry and spatial single-cell RNAseq
Cell-cell communication has traditionally been studied at the level of proteins in receptor-ligand interaction. Recently, we have identified cell-cell communication to depend on the exchange of metabolites that cause functional alterations in immune cells. Since the characterization of metabolites and lipids as mediators of cell-cell communication is impossible by protein-based technologies, we explore mass spectrometry to identify cell-cell communication within tissues. Using imaging mass spectrometry in close collaboration with the laboratory of Prof. Ron Heeren from the University of Maastricht, we study cell-cell interaction and communication in liver tissue. Combining targeted and untargeted approaches, we build cell type-specific metabolome and lipidome signatures characteristic for specific functional states of immune cell populations in tissues. Machine-learning-based analysis of the cell-cell communication between liver tissue cells and immune cells detected in situ will provide us with a new level of understanding of how immune responses are fine-tuned to the tissue microenvironment.
Understanding the immune pathology of infection with pandemic pathogens
The SARS-CoV-2 pandemic has demonstrated the urgent need to understand the mechanisms determining immunopathology to organs observed during severe COVID-19 but also in the long-term consequences of SARS-CoV-2 infections. Within an interdisciplinary consortium of scientists, we will characterize the molecular mechanisms associated with the development of immunopathology upon infection with pandemic pathogens, such as SARS-CoV-2 and influenza viruses. We will determine key immunopathology-associated pathways by combining expertise from molecular virology, multi-omics profiling of immune cell populations at transcriptome, proteome, and metabolome levels, and innovative bioinformatic AI-based analysis. In further work, we will employ the knowledge of these pathways to establish molecular markers predicting the development of immunopathology and to develop targeted immune therapies to curb infection-associated immunopathology.
Strengthening anti-bacterial immunity to prevent infection
Within the Center for Infection Prevention (link to ZIP when established), a Core Institute of the Technical University of Munich located at the School of Life Science on the research campus Weihenstephan, we develop novel strategies to prevent bacterial infection. Strengthening the anti-bacterial immune defense in border organs such as the gut, lung, and skin but also the liver is at the core of this interdisciplinary research approach. Preventing infections with multi-resistant bacteria in humans and livestock is possible to approach to diminish the threat of multi-resistant bacteria, which is considered a silent but dangerous pandemic threat.
Selected publications from the Knolle research group
1. Limmer A, Ohl J, Kurts C, Ljunggren HG, Reiss Y, Groettrup M, Momburg F, Arnold B, Knolle PA. Efficient presentation of exogenous antigen by liver endothelial cells to CD8+ T cells results in antigen-specific T-cell tolerance. Nat Med 2000, 6: 1348-1354. https://www.nature.com/articles/nm1200_1348
2. Huang LR, Wohlleber D, Reisinger F, Jenne CN, Cheng RL, Abdullah Z, Schildberg FA, Odenthal M, Dienes HP, van Rooijen N, Schmitt E, Garbi N, Croft M, Kurts C, Kubes P, Protzer U, Heikenwalder M, Knolle PA. Intrahepatic myeloid-cell aggregates enable local CD8(+) T cell proliferation and successful immunotherapy against chronic viral liver infection. Nat Immunol 2013, 14: 574-583. https://doi.org:10.1038/ni.2573
3. Böttcher JP, Schanz O, Wohlleber D, Abdullah Z, Debey-Pascher S, Staratschek-Jox A, Hochst B, Hegenbarth S, Grell J, Limmer A, Atreya I, Neurath MF, Busch DH, Schmitt E, van Endert P, Kolanus W, Kurts C, Schultze JL, Diehl L, Knolle PA. Liver-Primed Memory T Cells Generated under Noninflammatory Conditions Provide Anti-infectious Immunity. Cell Reports 2013, 3: 779-795. https://doi.org:10.1016/j.celrep.2013.02.008
4. Böttcher JP, Schanz O, Garbers C, Zaremba A, Hegenbarth S, Kurts C, Beyer M, Schultze JL, Kastenmuller W, Rose-John S, Knolle PA. IL-6 trans-Signaling-Dependent Rapid Development of Cytotoxic CD8(+) T Cell Function. Cell Reports 2014, 8: 1318-1327. https://doi.org:10.1016/j.celrep.2014.07.008
5. Böttcher JP, Beyer M, Meissner F, Abdullah Z, Sander J, Hochst B, Eickhoff S, Rieckmann JC, Russo C, Bauer T, Flecken T, Giesen D, Engel D, Jung S, Busch DH, Protzer U, Thimme R, Mann M, Kurts C, Schultze JL, Kastenmuller W, Knolle PA. Functional classification of memory CD8(+) T cells by CX3CR1 expression. Nat Commun 2015, 6: 8306. https://doi.org:10.1038/ncomms9306
6. Beyer M, Abdullah Z, Chemnitz JM, Maisel D, Sander J, Lehmann C, Thabet Y, Shinde PV, Schmidleithner L, Kohne M, Trebicka J, Schierwagen R, Hofmann A, Popov A, Lang KS, Oxenius A, Buch T, Kurts C, Heikenwalder M, Fatkenheuer G, Lang PA, Hartmann P, Knolle PA*, Schultze JL*. Tumor-necrosis factor impairs CD4(+) T cell-mediated immunological control in chronic viral infection. Nat Immunol 2016, 17: 593-603. https://doi.org:10.1038/ni.3399
7. Hackstein CP, Assmus LM, Welz M, Klein S, Schwandt T, Schultze J, Forster I, Gondorf F, Beyer M, Kroy D, Kurts C, Trebicka J, Kastenmuller W, Knolle PA*, Abdullah Z*. Gut microbial translocation corrupts myeloid cell function to control bacterial infection during liver cirrhosis. Gut 2017, 66: 507-518. https://doi.org:10.1136/gutjnl-2015-311224
8. Michler T, Kosinska AD, Festag J, Bunse T, Su J, Ringelhan M, Imhof H, Grimm D, Steiger K, Mogler C, Heikenwalder M, Michel ML, Guzman CA, Milstein S, Sepp-Lorenzino L, Knolle P, Protzer U. Knockdown of Virus Antigen Expression Increases Therapeutic Vaccine Efficacy in High-Titer Hepatitis B Virus Carrier Mice. Gastroenterology 2020, 158: 1762-1775 e1769. https://doi.org:10.1053/j.gastro.2020.01.032
9. Dudek M, Pfister D, Donakonda S, Filpe P, Schneider A, Laschinger M, Hartmann D, Huser N, Meiser P, Bayerl F, Inverso D, Wigger J, Sebode M, Ollinger R, Rad R, Hegenbarth S, Anton M, Guillot A, Bowman A, Heide D, Muller F, Ramadori P, Leone V, Garcia-Caceres C, Gruber T, Seifert G, Kabat AM, Malm JP, Reider S, Effenberger M, Roth S, Billeter AT, Muller-Stich B, Pearce EJ, Koch-Nolte F, Kaser R, Tilg H, Thimme R, Bottler T, Tacke F, Dufour JF, Haller D, Murray PJ, Heeren R, Zehn D, Bottcher JP, Heikenwalder M, Knolle PA. Auto-aggressive CXCR6(+) CD8 T cells cause liver immune pathology in NASH. Nature 2021, 592: 444-449. https://doi.org:10.1038/s41586-021-03233-8
10. Pfister D, Nunez NG, Pinyol R, Govaere O, Pinter M, Szydlowska M, Gupta R, Qiu M, Deczkowska A, Weiner A, Muller F, Sinha A, Friebel E, Engleitner T, Lenggenhager D, Moncsek A, Heide D, Stirm K, Kosla J, Kotsiliti E, Leone V, Dudek M, Yousuf S, Inverso D, Singh I, Teijeiro A, Castet F, Montironi C, Haber PK, Tiniakos D, Bedossa P, Cockell S, Younes R, Vacca M, Marra F, Schattenberg JM, Allison M, Bugianesi E, Ratziu V, Pressiani T, D'Alessio A, Personeni N, Rimassa L, Daly AK, Scheiner B, Pomej K, Kirstein MM, Vogel A, Peck-Radosavljevic M, Hucke F, Finkelmeier F, Waidmann O, Trojan J, Schulze K, Wege H, Koch S, Weinmann A, Bueter M, Rossler F, Siebenhuner A, De Dosso S, Mallm JP, Umansky V, Jugold M, Luedde T, Schietinger A, Schirmacher P, Emu B, Augustin HG, Billeter A, Muller-Stich B, Kikuchi H, Duda DG, Kutting F, Waldschmidt DT, Ebert MP, Rahbari N, Mei HE, Schulz AR, Ringelhan M, Malek N, Spahn S, Bitzer M, Ruiz de Galarreta M, Lujambio A, Dufour JF, Marron TU, Kaseb A, Kudo M, Huang YH, Djouder N, Wolter K, Zender L, Marche PN, Decaens T, Pinato DJ, Rad R, Mertens JC, Weber A, Unger K, Meissner F, Roth S, Jilkova ZM, Claassen M, Anstee QM, Amit I, Knolle P, Becher B, Llovet JM, Heikenwalder M. NASH limits anti-tumour surveillance in immunotherapy-treated HCC. Nature 2021, 592: 450-456. https://doi.org:10.1038/s41586-021-03362-0
11. Koerber N, Priller A, Yazici S, Bauer T, Cheng CC, Mijočević H, Wintersteller H, Jeske S, Vogel E, Feuerherd M, Tinnefeld K, Winter C, Ruland J, Gerhard M, Haller B, Christa C, Zelger O, Roggendorf H, Halle M, Erber J, Lingor P, Keppler O, Zehn D, Protzer U, Knolle PA. Dynamics of spike-and nucleocapsid specific immunity during long-term follow-up and vaccination of SARS-CoV-2 convalescents. Nat Commun 2022, 13: 153. https://doi.org:10.1038/s41467-021-27649-y
12. Wratil PR, Stern M, Priller A, Willmann A, Almanzar G, Vogel E, Feuerherd M, Cheng C-C, Yazici S, Christa C, Jeske S, Lupoli G, Vogt T, Albanese M, Mejías-Pérez E, Bauernfried S, Graf N, Mijocevic H, Vu M, Tinnefeld K, Wettengel J, Hoffmann D, Muenchhoff M, Daechert C, Mairhofer H, Krebs S, Fingerle V, Graf A, Steininger P, Blum H, Hornung V, Liebl B, Überla K, Prelog M, Knolle PA*, Keppler OT*, Protzer U*. Three exposures to the spike protein of SARS-CoV-2 by either infection or vaccination elicit superior neutralizing immunity to all variants of concern. Nature Medicine 2022, 28: 496-503. https://doi.org:10.1038/s41591-022-01715-4
13. Hackstein CP, Spitzer J, Symeonidis K, Horvatic H, Bedke T, Steglich B, Klein S, Assmus LM, Odainic A, Szlapa J, Kessler N, Beyer M, Schmithausen R, Latz E, Flavell RA, Garbi N, Kurts C, Kummerer BM, Trebicka J, Roers A, Huber S, Schmidt SV, Knolle PA*, Abdullah Z*. Interferon-induced IL-10 drives systemic T-cell dysfunction during chronic liver injury. Journal of Hepatology 2023. https://doi.org:10.1016/j.jhep.2023.02.026
Selected reviews from the Knolle research group
- Knolle PA, Gerken G. Local control of the immune response in the liver. Immunol Rev 2000, 174: 21-34.
- Kern M, Popov A, Kurts C, Schultze JL, Knolle PA. Taking off the brakes: T cell immunity in the liver. Trends in Immunology 2010, 31: 311-317. https://doi.org:S1471-4906(10)00079-7 [pii] 10.1016/j.it.2010.06.001
- Kurts C, Robinson BW, Knolle PA. Cross-priming in health and disease. Nat Rev Immunol 2010, 10: 403-414. https://doi.org:nri2780 [pii] 10.1038/nri2780
- Thomson AW, Knolle PA. Antigen-presenting cell function in the tolerogenic liver environment. Nat Rev Immunol 2010, 10: 753-766. https://doi.org:nri2858 [pii] 10.1038/nri2858
- Protzer U, Maini MK, Knolle PA. Living in the liver: hepatic infections. Nat Rev Immunol 2012, 12: 201-213. https://doi.org:10.1038/nri3169
- Bottcher J, Knolle PA. Global transcriptional characterization of CD8 T cell memory. Seminars in Immunology 2015, 27: 4-9. https://doi.org:10.1016/j.smim.2015.03.001
- Wohlleber D, Knolle PA. The role of liver sinusoidal cells in local hepatic immune surveillance. Clin Transl Immunology 2016, 5: e117. https://doi.org:10.1038/cti.2016.74
- Tilg H, Adolph TE, Dudek M, Knolle P. Non-alcoholic fatty liver disease: the interplay between metabolism, microbes and immunity. Nat Metab 2021, 3: 1596-1607. https://doi.org:10.1038/s42255-021-00501-9
Yahoo N, Dudek M, Knolle P, Heikenwalder M. Role of immune responses for the development of NAFLD-associated liver cancer and prospects for therapeutic modulation. Journal of Hepatology 2023. https://doi.org:10.1016/j.jhep.2023.02.033
The full list of our publications can be found here on Pubmed.
We acknowledge the funding of our research projects by the German National Science Foundation (DFG), the German Center for Infection Research (DZIF) Munich site, the Ministry for Education and Research of Germany (BMBF), the Free State of Bavaria and the European Union.