A receptor/cytoskeletal movement triggered by costimulation during T cell activation

During T cell activation, the engagement of costimulatory molecules is ofte n crucial to the development of an effective immune response, but the mecha nism by which this is achieved is not known. Here, it is shown that beads a ttached to the surface of a T cell translocate toward the interface shortly after the start of T cell activation. This movement appears to depend on m yosin motor proteins and requires the engagement of the major costimulatory receptor pairs, B7-CD28 and ICAM-1-LFA-1. This suggests that the engagemen t of costimulatory receptors triggers an active accumulation of molecules a t the interface of the T cell and the antigen-presenting cell, which then i ncreases the overall amplitude and duration of T cell signaling.