Date of Award

Fall 2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Chemical and Biomolecular Engineering

First Advisor

Daniel A. Hammer

Abstract

Dendritic cells (DCs) are potent initiators of the adaptive immune response. Their trafficking from sites of inflammation to lymphoid tissue is essential to their function. Exactly how dendritic cells integrate multiple chemotactic cues to organize an accurate migratory path is not fully understood. We first characterize DC random motility (chemokinesis) on extracellular matrix proteins in the presence of chemokines. Then, using a microfluidic device, we present both single and competing chemokine gradients to murine bone-marrow derived DCs in a controlled, time-invariant microenvironment. We show that in counter gradients, CCL19 is 10 to 100 fold more potent than other chemokines CCL21 or CXCL12. Interestingly, when the chemoattractive potencies of opposing gradients are matched, cells "home" to a central region in which the signals from multiple chemokines are balanced. These results provide fundamental insight into the processes that DCs use to migrate toward and position themselves within secondary lymphoid organs. We extended this work to a combination of the microfluidic gradient generator and micropost array detectors to develop a novel method for probing traction forces during chemotaxis. We find DC migration is driven by short-lived traction stresses at the leading edge or filopodia. We illustrate that spatiotemporal pattern of traction stresses can be used to predict changes in the direction of DC motion. Additionally, we determine the characteristic duration of local dendritic cell traction forces and correlate this duration with force. Overall, DCs show a mode of migration distinct from both mesenchymal cells and other leukocytes, characterized by rapid turnover of traction forces in leading filopodia. In this thesis, we extend the current understanding of DC motility to include signal integration and traction forces.

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