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10 May 1996 Polarized T-cell sensitivity to antigen revealed with an optical trap
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T-cell contact with antigen-presenting B cells initiates an activation cascade which includes an increase in T-cell [Ca2+] and leads to T-cell differentiation and proliferation. We evaluated cell-cell contact requirements for T-cell activation by using an optical trap to control the orientation of T-cell/B-cell pairs and fluorescence microscopy to measure subsequent T-cell [Ca2+] responses. B cells were trapped with a titanium-sapphire laser tuned to 760 nm and placed at various locations along the T cells, which had a polarized appearance defined by shape and the direction of crawling. T-cell intracellular [Ca2+] was detected as an emission shift from the combination of fura-red and fluo-3, two cytoplasmic [Ca2+] indicators. T cells which were presented antigen at the leading edge had a higher probability of responding (84% vs. 31%) and a shorter latency of response (42 s vs. 143 s) than those contacting B cells with their trailing end. Similar results were obtained using beads coated with antibodies to the T-cell receptor. These findings demonstrate a role for initial T-cell/B-cell contact geometry in T-cell activation by showing that the T cell is a polarized antigen sensor.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Paul A. Negulescu, Tatiana B. Krasieva, Bruce J. Tromberg, and Michael D. Cahalan "Polarized T-cell sensitivity to antigen revealed with an optical trap", Proc. SPIE 2678, Optical Diagnostics of Living Cells and Biofluids, (10 May 1996);

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