Liver Immunology group
Lab head: Patrick Bertolino
Location: Liver Immunology Program, Centenary Institute
Liver Immunology: The liver has fascinating immunological properties. In animal models of transplantation, livers grafted across MHC barriers do not result in rejection and are able to prevent rejection of a different organ from the same donor, suggesting that the liver has induced donor-specific tolerance. This bias toward tolerance is advantageous in transplantation as it promotes graft acceptance. However, it can be detrimental when pathogens infecting the liver, such as malaria, Hepatitis B and C viruses, induce tolerance and evade immune responses, leading to chronic infection. Understanding how the liver induces tolerance will reveal new strategies to boost immune responses to clear liver pathogens, or to increase the survival of solid organ transplants.
Research in the group: Our group is recognized internationally for contributions to this field. Using a variety of transgenic mouse models, we were the first to demonstrate that naïve CD8 T cells can be directly activated in the liver. We have now evidence that the liver can also support activation of naïve CD4 T cells. These are unique findings, as it was thought that naïve T cells could only be activated in lymphoid organs. We showed that unlike CD8 T cells activated in lymphoid tissues, liver-activated T cells die by apoptosis, leading to tolerance. The fate of CD4 T cells activated in the liver is totally unknown. Recently, we discovered a different mechanism that the liver uses to delete liver-activated CD8 T cells. This mechanism was very efficient, resulting in rapid clearance of T cells within a few hours. T cells were found to invade hepatocytes (the main liver cells), and were subsequently degraded within lysosomal compartments. This is a novel cellular phenomenon, which will open up new ways to understand immune cell regulation by the liver. The two projects available in our group for 2015 will use a new generation of recombinant adeno-associated virus (AAV) vectors able to transduce 100% of mouse hepatocytes in vivo. These recently developed vectors represent new powerful tools to investigate the phenotype, function and fate of T cells activated intrahepatically.
Funding: approx 500K per year
Project 3 (2014): Analysing recirculation of CD4 and CD8 T cells after primary T cell activation in the liver
Primary supervisor: Patrick Bertolino
Background and aims: The liver is exceptionally able to act as a site of primary CD4 and CD8 T cell activation in the absence of lymphoid tissues. Although most T cells activated in the liver are deleted, some T cells survive. These cells initially in the blood, cross the endothelial barrier and infiltrate the liver while proliferating. Although some of these T cells are found in the liver at 48h post-T cell transfer, some cells reach liver draining lymph nodes. This is a blood-lymph translocation that is unique amongst solid tissues as all other organs do not support primary activation of naïve T cells. It is unclear whether T cells reaching the lymph drainage are different from those remaining in the liver and whether they acquire a different phenotype once they reach the lymph nodes. The path used by these T cells to reach the lymph nodes is also unknown. Our group has acquired solid data and possesses powerful tools to address these fundamental questions.
1. Perform kinetics to analyse the path taken by fluorescently tagged transgenic T cells following primary activation in the liver of mice with restricted antigen expression on hepatocytes. This will be analysed on liver sections by immunofluorescence.
2. Analyse by flow cytometry the phenotype of T cells in the liver and draining vs non draining LNs at different time points to understand the sequence of events leading to the blood-lymph T cell translocation.
3. Isolate the transgenic T cells from liver and draining LNs of recipient mice and adoptively transfer them in a secondary host to determine whether they share similar survival and migration properties.
Expected outcomes: We hypothesize that T cells that have escaped deletion and managed to reach the lymph nodes will have a different phenotype and survive better than T cells isolated from the liver. It is likely that these T cells will contribute to the pool of T cells that persist in these mice several months after T cell transfer.
Why is this project important? Primary T cell activation in the liver is unique amongst solid organs and understanding T cell recirculation in this organ is relevant to the setting of different chronic infections by pathogens that target this organ (hepatitis B and C, malaria, etc). In addition all T cells go through the liver many times a day. Translocation via the liver tissue might be a common path used by activated T cells to reach the lymph. It is also tempting to speculate that this translocation shapes the T cell response and memory by trimming unsuitable effector T cells.
Techniques you will learn for the project: This project will give you experience in mouse handling and organ harvesting; multicolour flow cytometry; immunohistochemistry; and confocal microscopy. Experience in these techniques are invaluable for a career in immunology research. You will use recombinant AAV vectors that are currently in clinical trials for gene therapy in a range of conditions. There is potential for both projects to evolve into a PhD research project for the right candidate.
Discipline: Infectious diseases and Immunology
Co-supervisors: Frederic Sierro, David Bowen
Keywords: Transgenic mouse models, tolerance, transplantation, AAV vectors, gene therapy, T-cells