Figure 3.

A microsynapse composed of a core TCR–MC and a surrounding micro adhesion-ring. (A) time course of microsynapse generation, (B) molecular assembly in the microsynapse. Immediately after TCR–MCs are formed, an adhesion-ring composed of integrin LFA-1 and focal adhesion molecules such as Paxillin and Pyk2 is generated around the TCR–MC. Because the structure resembles the mature Immunological Synapse in a micro scale, this structure was designated the microsynapse. The adhesion-ring is dependent on LFA-1 outside-in signaling and is supported by F-actin and Myosin II. Cluster formation by LAT and SLP76, but not the TCR or ZAP70, is supported by the microsynapse. The adhesion-ring is a transient structure and disappears before cSMAC formation. The microsynapse is sustained upon weak TCR stimulation, whereas it disappears quickly upon strong stimulation, suggesting that it functions to augment the TCR activation signal upon weak stimulation.