Dendritic cells (DCs) form a key component of the immune response, as they are involved in the
innate and adaptive immunity and in the process of tolerance. Under normal conditions, DCs are
absent from the Central Nervous System (CNS), as the blood brain barrier (BBB) restricts their
entry. However, DCs have recently been implicated in the pathogenesis of several CNS
diseases. The molecular mechanisms that mediate DC trafficking across the BBB are poorly
understood. The objectives of this study were to examine the role of endothelial cell adhesion
molecules (eCAMs) and their ligands in the process of DC adhesion to the BBB endothelium,
and to investigate the participation of DCs in human CNS diseases. To study DC adhesion, DCs
were generated in vitro by culturing human blood monocytes in the presence of GM-CSF and IL-
4, and DC maturation was induced by adding inflammatory cytokines (TNF-α, IL-1β, IL-6) and
PGE₂. Immature and mature DCs displayed differences in their expression of surface molecules,
including eCAM ligands, by flow cytometry. Adhesion to the cerebral endothelium was
investigated using an in vitro model of the BBB consisting of primary cultures of human brain
microvessel endothelial cells (HBMEC). Immature or mature DCs were incubated with resting
or TNF-α-activated HBMEC for up to one hour. Only a few DCs adhered to resting HBMEC,
but adhesion was upregulated upon activating HBMEC (p<O.Ol). Moreover, immature DCs
adhered to activated HBMEC to a greater extent compared to mature DCs (p<O.OOl). Blocking
experiments indicated that the adhesion of both immature and mature DCs to HBMEC was
dependent upon ICAM-1-CD18 or ICAM-2-CD18, ICAM-2-DC-SIGN, and PECAM-l
PECAM-l interactions. In addition, VCAM-1-VLA-4 interactions mediated the adhesion of
immature but not mature DCs to activated HBMEC. Using immunohistochemistry for DC
markers, we also examined the presence of DCs in human inflammatory, infectious, and
neurodegenerative diseases, stroke and tumours. The results indicate accumulation of DC
SIGN—, fascin—, and MHC class Il—expressing DCs in the CNS under most pathological
conditions. These findings provide further insight into the mechanisms of neuroinflammation,
and highlight the role of DCs and the BBB endothelium in this process.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/5029 |
| Date | 11 1900 |
| Creators | Arjmandi Rafsanjani, Azadeh |
| Publisher | University of British Columbia |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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