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Beta chemokine expression and regulation of lymphocyte traffic at the blood-brain barrier

University of British Columbia

The blood-brain barrier (BBB) formed by the endothelial lining of the cerebral vasculature contributes to the relative immunologic isolation of the brain. The BBB is compromised in ischemic, traumatic, infectious, inflammatory and autoimmune diseases resulting in increased permeability and leukocyte entry into the CNS. The chemokines RANTES (regulated upon activation normal T cell expressed and secreted) and MIP-lβ (macrophage inflammatory protein Iβ) have been implicated in the subset-specific chemoattraction and activation of memory and activated CD4+ T lymphocytes respectively. The presence of these chemokines in inflammatory brain lesions suggests a role in subset-specific lymphocyte trafficking which has not been previously explored. The objective of this study was to characterize the expression of RANTES and MIP-1β by human brain microvessel endothelial cells (HBMEC) in vitro and to investigate their role in mediating T cell adhesion and migration across HBMEC monolayers. HBMEC were induced by pro-inflammatory cytokines and lipopolysaccharide (LPS) to secrete and bind to their surface RANTES and MIP-1β, suggesting chemokine availability for interactions with lymphocytes. The ability of RANTES and MIP-1β to attract specific lymphocyte subsets across HBMEC monolayers was studied in a double chamber chemotaxis system. After establishing chemokine gradients across the monolayers, resting, anti-CD3 activated, memory and naive CD4+ T cells were added to the upper chamber and incubated with HBMEC for one to three hours. Concentration gradients of RANTES or MIP-1β stimulated significant in vitro adhesion and migration of resting, memory, antigen-specific, and activated T cells but not naive T cells. Chemotaxis was observed only in the presence of cytokine-activated HBMEC. The chemokine enhanced adhesion and migration were dependent upon integrins and EC adhesion molecules. Thus, neutralizing antibodies (mAb) to intercellular adhesion molecule-1 (ICAM-1) significantly reduced adhesion and migration of both resting and activated CD4+ T cells. mAb blocking of vascular cell adhesion molecule-1 (VCAM-1) and α4 integrin (the α subunit of VLA-4) also reduced the chemokine-enhanced adhesion and migration of activated T cells. These studies indicate that RANTES and MIP-1β have chemoattractant as well as activating effects on T lymphocyte subsets, suggesting an important role of these chemokines in regulating lymphocyte subset-specific trafficking across the BBB.

Thesis/Dissertation

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2009-07-02

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http://hdl.handle.net/2429/10003

Pathology

University of British Columbia

UBCV

DSpace