Imaging the immune synapse: Three-dimensional analysis of the immune synapse.

T cell receptor (TCR) stimulation of T lymphocytes by antigen bound to the major histocompatibility complex (MHC) of an antigen-presenting cell (APC), together with the interaction of accessory molecules, induces the formation of the immunological synapse (IS), the convergence of secretion vesicles toward the centrosome, and the polarization of the centrosome to the IS. Upon IS formation, an initial increase in cortical filamentous actin (F-actin) at the IS takes place, followed by a decrease in F-actin density at the central region of the IS, which contains the secretory domain. These reversible, cortical actin cytoskeleton reorganization processes that characterize a mature IS occur during lytic granule secretion in cytotoxic T lymphocytes (CTL) and natural killer (NK) cells and cytokine-containing vesicle secretion in T-helper (Th) lymphocytes. Besides, IS formation constitutes the basis of a signaling platform that integrates signals and coordinates molecular interactions that are necessary for an appropriate antigen-specific immune response. In this chapter we deal with the three-dimensional (3D) analysis of the synaptic interface architecture, as well as the analysis of the localization of different markers at the IS.