Leukocyte trafficking; immunity; lymphatic vessels; vascular biology
Tiefenboeck P, Kim JA, Trunk F, Eicher T, Russo E, Teijeira A, Halin C, Leroux JC (2017), Microinjection for the ex Vivo Modification of Cells with Artificial Organelles, in ACS Nano
, 11(8), 7758-7769.
Teijeira M, Hunter M, Russo E, Proulx ST, Frei T, Debes G, Coles M, Melero I, Detmar M, Rouzaut A, Halin C (2017), T Cell Migration from Inflamed Skin to Draining Lymph Nodes Requires Intralymphatic Crawling Supported by ICAM-1/LFA-1 Interactions, in Cell Reports
, 18(4), 857-865.
Hunter M, Teijeira A, Halin C (2016), T Cell Trafficking through Lymphatic Vessels, in Front Immunol
, 7, 613.
Russo E, Teijeira A, Vaahtomeri K, Willrodt AH, Bloch J, Nitschké M, Santambrogio L, Kerjaschki D, Sixt M, Halin C (2016), Intralymphatic CCL21 Promotes Tissue Egress of Dendritic Cells through Afferent Lymphatic Vessels, in Cell Reports
, 14(7), 1723-1734.
Teijeira A., Halin C. (2015), Editorial: Breaching their way through: Neutrophils destroy intercellular junctions to transmigrate rapidly across lymphatic endothelium, in Journal of Leukocyte Biology
, 98(6), 880-882.
Afferent lymphatic vessels (LVs) fulfill important immune functions by transporting soluble antigen and leukocytes, such as dendritic cells (DCs) or recirculating CD4+ T cells, to draining lymph nodes (dLNs). Especially the migration of DCs from peripheral tissues to dLNs is well-known to be essential for sustaining peripheral tolerance or for promoting immune responses against pathogens. Performing intravital microscopy (IVM) in the murine ear skin our group has recently reported that DCs actively crawl within afferent lymphatic capillaries and appear to only be passively drained by flow once they reach downstream collecting vessels. Interestingly, DC migration within LV capillaries resembled a vascular patrolling behavior; while some intralymphatic DCs remained immotile for long time periods, the majority migrated in a semi-directed fashion within lymphatic capillaries (i.e. taking frequent turns). The Overall Aim of this proposal is to further characterize the mechanism and functional significance of leukocyte migration and behavior within afferent LVs. For example, we plan to investigate the mechanisms that promote directed crawling of intralymphatic DCs in downstream direction of the dLN. Using IVM we have compiled preliminary evidence that CCL21 is involved in this process and hypothesize that an intralymphatic CCL21 gradient, deposited by the lymph flow, guides DCs in downstream direction. In Subproject A we therefore plan to determine whether CCL21 regulates the directionality of intralymphatic DC migration, as suggested by our preliminary data. This will be addressed by performing IVM or time-lapse imaging in skin explants, as well as in vitro flow chamber studies. Another sub-aim of this proposal is to investigate whether the patrolling / arresting behavior of DCs within lymphatic capillaries has a functional significance in the immune response. Given that the majority of leukocytes migrating through afferent LVs reportedly are CD4+ T cells, we hypothesize that DCs might be interacting with these cells and might already be fulfilling antigen-presenting functions within LVs. In Subproject B we therefore plan to determine whether intralymphatic DC-T cell interactions occur and to investigate the immunologic significance of such interactions. These aims will be addressed using various gene-targeted mouse strains, amongst them T cell receptor (TCR)-transgenic mice and fluorescent reporter mice, in combination with IVM or ex vivo analyses. Finally, in Subproject C, we plan to identify new genes involved in leukocyte migration within lymphatic vessels and to correlate gene expression in lymphatic capillaries and collectors with differences in the mode of leukocyte migration in these two vessel segments (i.e. crawling vs. flowing). To this end, we will perform a comprehensive gene expression analysis of lymphatic endothelial cells (LECs) isolated by FACS-sorting from dermal LV capillaries or collectors. Overall, our project will generate fundamental new insights into the process of leukocyte migration within LVs - a migratory step that has been much less well characterized as compared to leukocyte trafficking through blood vessels (BVs). In addition to establishing the molecular mechanism of this process, the project will investigate whether afferent LVs represent a compartment in which DCs and T cells interact and adaptive immune responses are induced or modulated. A confirmation of this concept would significantly change and extend the current perspective on the role that LVs play in the immune response.