Fig. 6. Models of immunological synapses and a kinapse. (A)The bull's-eye model of an IS comprises three concentric zones. The cSMAC contains concentrated TCRs and PKC, and is where signalling is terminated. The surrounding pSMAC contains LFA-1 and talin. The dSMAC is enriched in the phosphatase CD45, which is excluded from the synapse to maintain optimal signalling. (B) The zones of the multifocal synapse are less-well defined. The synaptic interface contains many cSMACs, and the LFA-1-rich pSMAC is diffuse. (C) The kinapse represents a migrating cell that forms transient synapses. PKC mediates the transition from a stationary IS to a kinapse, whereas WASp mediates the reverse action. As with both the bull's-eye and multifocal models, signalling microclusters form in the distal area (dSMAC) and move through the pSMAC to the cSMAC, where signalling is terminated. In the polarised cell, the dSMAC corresponds to the lamellipodium, the pSMAC to the mid-region and the cSMAC to the uropod.