Dendritic cells and control of T cell immune responses
DCs are unique antigen-presenting cells that can initiate (prime) CD4 T cell responses, as well as controlling the progression and subsequent reduction of the immune response, development of immunologic memory and activation of other cell types such as macrophages and B cells.
Professor Barbara Fazekas.
Camperdown - Centenary Institute
The interaction between dendritic cells (DCs) and CD4 T cells lies at the heart of the immune response. Although many different DC subsets and activation states have been defined, we do not yet understand the particular role of each subset, nor how they interact in vivo. In vitro analysis, while helpful in defining the ability of DCs to activate T cells, cannot accurately reproduce many of the different functional states achieved by CD4 T cells (such as deletion, anergy, suppression, effector and central memory). Our laboratory has developed a set of unique transgenic mouse models that allows us to test the outcomes of interaction between CD4 T cells and defined subsets of DCs in vivo. In these models, we restrict antigen presentation to particular DCs by restricting expression of antigen-binding MHC class II molecules. In addition, we have expressed our model antigen in a number of forms with different immunological effects: as a self-antigen (leading to deletion or differentiation of specific regulatory T cells), as part of a soluble fusion protein, used to induce tolerance, allergy, or memory, depending on how it is administered, and as part of Mycobacterium tuberculosis, a pathogenic organism that is a major cause of human infection. By testing each type of antigen with each subset of DCs, we are building a picture of how the range of CD4 T cell responses is controlled. Using these models, we have been able to show that some DC subsets are able to induce T cell proliferation without supporting the generation of memory T cells, whereas others support memory development. In addition, we have defined different responses of DC subsets to in vivo stimuli such as contact with microbes.
Research topics for PhDs: Migration, activation and function of defined DC subsets.
- Flow cytometry (FACS) - the Centenary Institute has a world-class flow cytomety facility with over $3M of sorting and analysis equipment. We routinely perform 8-9 colour sorting and analysis.
- Intravital microscopy - the Centenary Institute is purchasing a state-of-the-art 2-photon intravital microscope in mid 2007
- Confocal microscopy - the Centenary Institute is purchasing a state-of-the-art confocal microscope in mid 2007
- Transgenic and knockout mice - the Centenary Institute has an outstanding track record of making and using genetically manipulated mouse strains. The on-site animal facility is an Australian leader in mouse husbandry and complex breeding.
Efficacy of vaccination depends, among other factors, on the route of antigen administration. Using our very own mouse model that allows tracking of defined DC subsets in vivo
, we are studying DC migration from peripheral sites of antigen uptake (e.g. skin) to the draining lymph nodes where CD4 T cell priming takes place. When DCs loaded with a model antigen arrive in the lymph node, they can activate a very small trace population of antigen-specific CD4 T cells, allowing us to measure DC function in vivo
by means of their effect on the CD4 T cells. Alternatively, we isolate DCs from the lymph nodes by means of cell sorting (FACS), and their ability to activate antigen-specific CD4 T cells is subsequently measured in vitro
using a T cell proliferation assay. It appears that DC migration and DC activation are linked in a DC subset-specific manner. Some high-throughput methods (RNA arrays) and in vivo
imaging (confocal and intravital microscopy) are on our “to do” list. Role of dendritic cell subsets in the initiation and maintenance of CD4 T cell responses.
Are all DCs equal? It appears that “some are more equal than others”! Using our unique mouse model, we can restrict antigen presentation in vivo to defined subsets of DCs (this is done by restricting the expression of the antigen-binding MHC class II molecules). We then study the behaviour of a very small trace population of antigen-specific CD4 T cells. We have interesting preliminary data suggesting functional differences between DC subsets in vivo
. Some DCs but not others can support the generation of functional T cell memory! If you want to know more, come and talk to our dynamic team!
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The opportunity ID for this research opportunity is 216
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Professor Barbara Fazekas