The organization of the immunological synapse formed at the interface between an antigen-presenting cell (APC) and a responding T cell. Engagement of the TCR with peptide-MHC on the APC surface results in peptide-MHC signaling within the APC. Interaction of the costimulatory receptor CD28 with its ligands, which results in secondary signaling, is enhanced in the central region of the immunological synapse. Key effector molecules, such as the cytokine IL-4 and the inhibitory protein CTLA-4, delivered to the central area by exocytosis, limit effects on bystander cells. The immunological synapse may be required for internalization of TCRs, which may be one way that TCR signaling is down-regulated.