Imaging the Immune system: From Cancer to Pathogens
15 – 16 April 2009, Yorkshire Immunology Group & Hull/York Medical School, York, UK
Having never before encountered the phrases “exposed oak beams” and “two-photon intravital microscopy” within the same immunology talk, the recent meeting: ‘Imaging the Immune System: From Cancer to Pathogens’, held in the 650-year-old Merchant Adventurers Hall in York provided a unique opportunity to learn about advances in immunological imaging whilst enjoying the intimate setting of a beautiful historic building
Combining presentations from experts in areas as wide ranging as NK signalling and human dendritic cell-mediated cancer immunotherapy, the meeting showcased the variety of basic and clinical research to which modern imaging techniques are being applied.
The meeting kicked off with an interesting talk by Daniel Davis ( UK) covering synapses and nanotubes in immune-cell biology. Starting with some great videos showing the interactions of fluorescently labelled signalling proteins, the point was made that rather than the linear signalling cascades depicted in the textbooks, signalling is far more fluid and involves clusters of proteins moving between substrates, phosphorylating as they go. The talk then moved on to describe the intriguing membrane nanotubes that form between immune cells, including T cells and NK cells. Of particular interest were movies showing HIV-1 virus particles ‘surfing’ between T cells on such structures, as well as NK cells initiating cell death from some distance whilst tethered to a target cell by the membrane tubes.
Switching to two-photon imaging of thick thymic slices, Lauren Ehrlich ( USA ) gave an extremely clear presentation detailing her work on the migration and intrathymic location of thymocytes during T-cell development. Lauren presented striking videos which showed that whilst DN and DP thymocytes are restricted to migration within the thymic cortex, CD4SP cells accumulate in the thymic medulla and migrate more rapidly than their less differentiated counterparts. She went on to show evidence that the lack of DN and DP thymocytes in the medulla was due to an inability to migrate on cortical substrates rather than being directly blocked at the corticomedullary junction. Finally she described that CD4SP thymocyte entry to the medulla is via a G-protein coupled receptor mechanism but not solely due to CCR 7 expression on these cells; the thymic medulla of CCR 7-/- mice still have CD4SP cells, although these are reduced in frequency when compared to wild type animals.
Ron Germain ( USA ) was next to present, with a snapshot of the work currently underway in his lab, with interesting findings related to the role of SAP in T- and B-cell interactions and some unpublished observations on the dynamics of antigen-specific CD4+ T cells within BCG-induced hepatic granulomas.
After a novel description of multi-colour electron microscopy from Peter O’Toole ( UK ), the meeting then shifted direction, by focussing on cancer biology and the imaging of anti-cancer responses. First up was Kevin Brindle ( UK ) who presented work on ground-breaking new technology for imaging the responses of tumours to anti-cancer drugs in cancer patients. These techniques, which use a combination of magnetic resonance imaging with new methods for achieving ‘nuclear-spin hyperpolarisation’, allow the detection of cell death in vivo.
Describing his work on lymphocyte motility in vivo Jens Stein ( Switzerland ), presented some interesting data on the invasion of a dense HEV network into the T-cell zone during lymph node inflammation utilising optical projection tomography. Philippe Bousso ( France ) went on to present a very interesting study of NK-cell activation and cytotoxic-T-cell anti-tumour function in vitro and in vivo. Videos showing a clear propensity for CTL to form stable contacts with DC were in contrast to those showing the far higher motility and the lack of stable contacts formed when NK cells were imaged. OTI CTL were shown to interact strongly with tumour cells, proliferating and migrating after such cells had been killed. Finally in an extraordinary video, the precise point at which target cell killing occurs was visualised utilising a caspase 3-dependent YFP/GFP switch whilst imaging a CTL /tumour cell conjugate. A lively discussion followed this presentation, focusing on whether or not stable NK:DC interactions were in fact being missed by the inevitable limitations in imaging time.
The next theme of the meeting was host–pathogen interactions and began with a talk from Matthias Gunzer ( Germany ) regarding invasive aspergillosis and innate immunity which included an innovative methodology by which to image the long bones of experimental mice. After describing the differential ability of DC and neutrophils to phagocytose fungal spores in 2D- or 3D culture, intravital two-photon images of the tibial bone in CX3CR-GFP mice were presented. These clearly showed that macrophages were more motile than DC within the bone marrow and that DCs more closely associate with the endosteum. In addition, neutrophil migration out of the bone marrow as well as evidence that systemic administration of a CXCR2 ligand dramatically increased neutrophil motility and extravasation into the blood.
Applying imaging techniques to another infectious disease, Paul Kaye ( UK ) then discussed the ways in which imaging technologies may help the development of new therapeutics to treat infection with Leishmania donovani. Recent data from his lab was presented, including that showing the behaviour of CD8+ T cells in Leishmania-induced hepatic granuloma as well as the restoration of lymphoid tissue structure after treatment with anti-angiogenic drugs.
James Brewer ( UK ) had interesting data to present regarding the application of 2-photon imaging to the understanding of how dendritic cells cause immune-suppression following Plasmodium infection and shared a lesson with the audience about the fact that not all fluorescent proteins behave the same under 2-photon conditions as they do when used for standard fluorescence microscopy.
This brought the meeting to the end of the first day, with interesting scientific discussions continuing over the pre-dinner canapés and dinner served in the amazing and atmospheric surroundings of the merchant adventures hall.
The following morning saw talks from the principal organiser of the meeting Mark Coles
(UK)who presented work on cell migration in thymus development and the developmental organisation of lymph-node stroma. Next, Neil Carragher
( UK ) from AstraZeneca wowed the audience with a demonstration of the resources available in the pharmaceutical industry for the application of new imaging technologies in his talk entitled: ‘What does pharma want to get from imaging?’
Erik Sahai ( UK ) utilised two-photon microscopy to visualise the metastatic process during breast cancer. His data revealed a potential role for TGF-β in the metastasis of established tumours and suggested that metastasising tumour cells were more motile than those resident within tumours.
Continuing the tumour biology theme, Matthew Krummel ( USA ) described a distinct population of tumour-associated APC , coining them a ‘DC / Macrophage hybrid’ due to their simultaneous expression of CD11c, MHCII and F4/80. Such cells were shown to express co-stimulatory molecules but actively suppress T-cell proliferative capacity. This was deemed to be independent of CTLA-4, PD-1 or arginase activity. These apparently suppressive APC seemed to accumulate at the periphery of established tumours and readily interacted with T cells, particularly when presenting tumour antigen.
Jumping organisms to data based on human clinical trials, Carl Figdor ( Netherlands ) described innovative methods to track dendritic cells after injection during cancer-immunotherapy treatment. The meeting was rounded off by a talk from Christopher Contag ( USA ) on the in vivo imaging of mice and humans in order to guide cellular therapies to cancer.
Overall the meeting provided an excellent insight into the spectrum of imaging techniques available to the immunologist, and included fantastic talks on a wide range of topics. The organisers clearly put in a huge amount of effort to get things arranged so smoothly and deserve much credit for supplying an exciting meeting in such a beautiful venue.
Benjamin Owens & Lynette Beattie , Centre for Immunology and Infection, Hull York Medical School & Department of Biology, University of York , UK