The lymphatic system provides a conduit for the trafficking of immune cells from the periphery to draining lymph nodes, both for constitutive immune surveillance and during inflammation. Thus, leucocyte migration into the lymphatics represents an important step in the initiation of a primary immune response, which occurs within lymph nodes. Traditionally, it has been considered that neutrophils are absent from the afferent lymph, having a finite lifespan in the periphery after extravasation from the blood. However, recent research has reported the presence of neutrophils in lymph nodes, in animal models of infection, where neutrophil trafficking was found to occur through afferent lymphatic vessels. This thesis examines the mechanisms regulating neutrophil migration, both by the lymphatic endothelium and neutrophils themselves, under resting and inflammatory conditions. Primary human dermal lymphatic endothelial cells (HDLECs) respond to the pro- inflammatory cytokine, TNF-α by instigating a distinct expression programme, characterised by the up-regulation of various adhesion molecules (ICAM-1, VCAM-1, E-selectin), and CXC- chemokines (ENA-78, GROβ, IL-8), as well as other potential regulators of neutrophil entry such as constitutively expressed adhesion molecules, CD99 and ESAM. Moreover, neutrophils possess counter-receptors for these adhesion molecules and contain basement membrane-specific proteases (elastase) and matrix metalloproteinases (MMPs) such as MMPs -8 and -9, localised in intracellular granules, ready to be exocytosed upon inflammatory stimuli. In vitro data presented in this thesis demonstrate that neutrophil adhesion and transmigration of the lymphatic endothelium is entirely dependent on prior activation of the monolayer with TNF-a. Furthermore, the aforementioned lymphatic-expressed adhesion molecules and chemokines, as well as neutrophil-derived proteases and MMPs are shown to play critical roles in neutrophil adhesion and transmigration of the lymphatic endothelium. Subsequent in vivo experiments confirmed that neutrophil trafficking to lymph nodes across lymphatic vessels is wholly dependent on prior vaccination with Mycobacterium bovis Bacillus Calmette-Guerin (BCG) Tokyo-172. Moreover, neutrophils trafficking to lymph nodes across lymphatic vessels are shown to require ICAM-1. The results described in this thesis provide the first evidence that both the lymphatic endothelium and neutrophils act in concert to regulate entry to lymph nodes and determine the outcome of infection, or vaccination.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:561107 |
| Date | January 2011 |
| Creators | Rigby, David Andrew |
| Contributors | Jackson, David |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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