Mapping the polarity for T-cell activation with an optical trap
Optical Investigations of Cells In Vitro and In Vivo
In the body, individual T helper lymphocytes need to be EtiVated first by physical contactwith antigen-presenting cells (APC). T-cell contact with APCs initiates an activation cascade which includes an increase in T-cell intracellular calcium and leads to T-cell proliferation and differentiation. We have combined fluorescence spectroscopy and imaging with optical manipulation to investigate the physical properties of T-cell activation. We study cell-cell contact requirements for T-celi
... for T-celi activation using optical tweezers to conirol the orientation of T-celI/APC pairs and fluorescence microscopy to measure the subsequent T-cell intracellular calcium level ([Cai1) response. APCs or beads coated with antibodies to the T-cell receptor trapped with a near-infrared titanium-sapphire laser and pled at different locations along the T-cell, which has a poliwized appearance defined by the shape and direction of crawling. T cells which are presented with antigen at the leading edge have a higher probability of responding and a shorter latency of response than those contacting APCs or beads with their trailing end. Alterations in antibody density and bead size are used to determine the spatial requirements for T cell activation and the minimum number of receptors which must be engaged in order to transmit a positive signal.