THE EFFECT OF CONFINEMENT ON T-LYMPHOCYTE UPSTREAM MIGRATION UNDER SHEAR FLOW
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Graduate group
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Engineering
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Microcontact printing
Microfluidics
Shear flow
T Lymphocytes
Upstream migration
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Abstract
To maintain homeostasis and fight infections, leukocytes must exit the bloodstream and reach sites of inflammation. The leukocyte adhesion cascade has evolved to perform this function. One step is migration on the endothelium. CD4+ T-lymphocytes migrate upstream on intracellular adhesion molecule-1 (ICAM-1). In this thesis, we explore the potential of this upstream migration to direct T cells confined within microcontact printed and microfluidic devices. In the first aim, we explore the microcontact printing conditions to confine T cells within printed ICAM-1 patterns and support upstream migration. We determined directly inking and printing a 50:50 mixture of ICAM-1 and vascular adhesion molecule-1 (VCAM-1) provides optimal conditions without creating any noticeable topological features. In the second aim, we seeded T cells on stripes oriented in the direction of flow and tested upstream migration. We discovered that confinement on stripes has the potential to inhibit upstream migration. T cells on 50μm stripes migrated primarily downstream. Full upstream migration was restored on stripes 200μm wide. Characterization of T cell migration determined that this behavior was a factor of the width of the patterned stripe. The edge of the printed stripe has a greater inhibition of upstream migration beyond that of the stripe width. In the third aim, we further investigated the phenomenon of induced downstream migration based on width of confinement by seeding T cells and observing migration under flow in microfluidic devices. Microfluidic channels with widths of 25μm and 50μm both resulted in downstream migration of T cells, confirming the discovery aim 2 across device architecture. Full upstream migration was restored in microfluidic channels 200μm wide. Characterization of T cell behavior within these devices determined that the downstream migration is regulated by the width of the channel. Interactions with the microfluidic wall has minimal additional inducement of downstream migration. The determination of T cell behavior dependent on the width of confinement discovered in this thesis may be applied to the creation of microfluidic devices to control and direct T cells for potential applications in immunotherapy.