@PhdThesis{diss_mods_00017292,
  author = 	{Li, Qian},
  title = 	{Adhesion studies of T-lymphocytes: insights into the adhesion dynamics of integrin-mediated inside-out signaling in response to TNF},
  year = 	{2015},
  publisher = 	{Christian-Albrechts-Universit{\"a}t zu Kiel},
  address = 	{Kiel},
  keywords = 	{T-lymphocytes; TNF; integrin; inside-out signaling},
  abstract = 	{Integrin-mediated T-lymphocyte adhesion to endothelial cells is a crucial step in the mammalian inflammatory response and for the elimination of pathogens. Outside-in signaling is the well-known pathway in the integrin-mediated leukocyte adhesion in response to proinflammatory events, which is stimulated by an important proinflammatory cytokine, the tumor necrosis factor (TNF). Many studies have been reported that TNF upregulates the expression level of endothelial cell surface molecules. This in turn activates the extracellular domain of integrins and thus facilitates the adhesion of T-lymphocytes both regarding biomolecular interactions and cell adhesion strength. Recently, an inside-out signaling pathway of integrins in lymphocyte activation by TNF has been brought up. However, how this activation modulates T-lymphocyte adhesion strength and dynamics is still not understood. In the study presented here, T-lymphocyte (Jurkat E6-1) cell adhesion to fibronectin (FN)-coated surface was investigated. Such surfaces provide a biomimetic environment since FN is naturally present on top of endothelium and additional effects from the surface molecules, which are present on endothelial cells in vivo, can be excluded. In detail, phase contrast microscopy and photonic crystal slabs (PCS) were applied for the quantification of cell amount and cell size on fibronectin as a function of TNF stimulation. No difference in these parameters was found for the cells with TNF stimulation compared to those without. An advanced optical strategy, reflection interference contrast microscopy (RICM), was applied for the measurement of the real cell adhesion area and the length of microspikes projected from the cell body. With this technique, cell adhesion dynamics and the fluctuation of subcellular structures were visualized, and again no significant effect of TNF stimulation was detected. To quantify the cell adhesion strength, single-cell force spectroscopy (SCFS) was employed to measure cell detachment forces and single ruptures dynamics. TNF significantly increased cell detachment forces and detachment energies, as well as the number of molecular ruptures and the force associated with single rupture events. Meanwhile, the most pronounced effect was obtained at the shortest cell-surface contact time of about 0.2 sec compared to the longest contact time of 10 sec. To understand the behavior of T-lymphocyte cells in the initial capture and rolling phase, microfluidics, which mimics the shear stress in in vivo situations, was used to track and analyze the percent of adhering cells and the speed of rolling cells as a function of TNF stimulation. The preliminary data show that TNF facilitates more cells to adhere on the surface and decreases the rolling speed. To obtain a detailed understanding of the integrin distribution and the proteins close to the adhesion site in T-lymphocyte cells, functionalized gold nanopatterned structures were used as substrates. No significant effect of TNF stimulation on the cell number or morphology was observed. Our results show that the TNF-stimulated inside-out-signaling pathway directly enhances T-lymphocyte adhesion, particularly cell adhesion strength.},
  url = 	{https://macau.uni-kiel.de/receive/diss_mods_00017292},
  file = 	{:https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00006165/dissertation_Qian_Li.pdf:PDF},
  language = 	{en}
}