TCR dynamics on the surface of living T cells

T lymphocyte activation by specific antigen requires prolonged TCR occupanc y and sustained signaling. This is accomplished by the formation of a speci alized signaling domain, the immunological synapse, at the T cell-antigen-p resenting cell contact site. Surface receptors and signaling components are progressively recruited into this domain where they are organized in defin ed three-dimensional structures. To better understand how TCR are supplied to the signaling domain during the activation process, we measured (using c onfocal microscopy and photo-bleaching recovery techniques) lateral mobilit y of GFP-tagged TCR on living Jurkat cell surface. We show that: (i) surfac e-expressed TCR exhibit an intrinsic, actin cytoskeleton-independent, later al mobility which allows them to passively diffuse over the entire T cell s urface within similar to 60 min and (ii) non-stimulated TCR rapidly enter t he signaling domain. Our results indicate that TCR lateral mobility per se is sufficient to ensure TCR supply to the immunological synapse in the cour se of sustained T cell activation.