Date of Award
Doctor of Philosophy (PhD)
Cell:cell interactions are critical at all stages of the immune response, yet relatively little is known about their dynamics in vivo. We set out to visualize in intact, living lymphoid tissue the physiological role of dendritic cells in tolerance and immunity; this was achieved by intravital microscopy of fluorescently-labeled DCs and lymphocytes in the inguinal lymph nodes. We generated mice that specifically expressed EYFP in their dendritic cells and observed their behavior in living LNs; we found that in the steady state, DCs formed sessile networks and largely restricted their movements to probing with their dendrites. We next observed dendritic cells’ interactions with transferred fluorescently labeled T cells under conditions of tolerance and immunity, and found both were characterized by similar activation, proliferation, and early antigen-dependent T cell arrest. Based on our initial observation that early tolerogenic and immunogenic interactions are similar, we investigated the role of TCR affinity for MHC:peptide complexes (pMHC) in these interactions during tolerance induction. We observed that pMHC potency correlates with T cell proliferation, Ca2+ flux and with early antigenspecific arrest; T cell anergy was induced by all ligands that activated T cells, and was independent of T cell proliferation, Ca2+ flux, and early arrest in vivo. We further examined the in vivo dynamics of germinal center reactions, and observed that germinal centers are dynamic structures, with nearly all GC B cells remaining motile and restricted to the germinal center, migrating bidirectionally between dark and light zones. Follicular B cells passed through the GC compartment easily, and were able to join ongoing GC reactions in an affinity-dependent fashion.
Lindquist, Randall L., "Visualizing Dendritic Cells In Vivo" (2008). Student Theses and Dissertations. 200.