The great majority of previous studies point to the inward movement of cortical F actin in the IS as the main or even sole driving force behind centripetal receptor bunch activity. On the basis of this statement and of the discoloration of the IS by using different antibodies, Dustin suggested that the IS is essentially a symmetrical model of the actin cytoskeleton at the top of a moving cell, where the dSMAC corresponds to the lamellipodium and the pSMAC corresponds to the lamellum. Implicit in this evaluation, therefore, is that the centripetal movement reversible Chk inhibitor of receptor groups could well be influenced by a combination of the pushing force provided by polymerization based actin retrograde actin movement in the LP and the pulling force provided by myosin II based contraction of transverse actin bundles inside the LM. Regarding the possible role of myosin II in the transportation of TCR MCs, an early study using blebbistatin to inhibit myosin II argued that the myosin isn’t needed for IS formation. In contrast, a subsequent review employing both BB and RNA interference knock-down of myosin IIA reported a dramatic inhibition of inward TCR MC movement, SMAC formation, and IS stability. Even though genuine in several features, this study didn’t picture the character of F actin or myosin II, determine the effect of myosin Urogenital pelvic malignancy II inhibition on the rate of actin flow, define the organization of F actin within the LM/pSMAC, or determine the site of action of myosin II within the IS. Furthermore, it didn’t parse out the relative contributions produced by actin retrograde flow and myosin II based contraction to the centripetal transport of TCR MCs. Armed with a novel reporter for F actin, we sought here to handle these and related unresolved questions about the position of the actin cytoskeleton in IS formation. 1 Jurkat T cells activated by ubiquitin-conjugating glass supported planar lipid bilayers containing ICAM 1 and anti CD3 antibody. Anti CD3 antibody labeled with rhodamine X and attached to biotinylated fats in the bilayer using a streptavidin link blows evenly in bilayers. Moreover, utilization of fluorescence recovery after photobleaching to assess the lateral mobility of ICAM 1 marked with Alexa 647 and attached to the bilayer via nitrilotriacetic acid conjugated lipids indicated the lipids in these bilayers are diffusing openly and uniformly. Finally, after 5 min of engagement with the bilayer, the great majority of Jurkat T cells formed the main accumulation of TCR MCs, as inferred from the distribution of the anti CD3 antibody in the bilayer, and the peripheral accumulation of the integrin LFA 1, as inferred from the distribution of ICAM 1 in the bilayer, which is characteristic of the bulls eye patterned IS formed by primary T cells destined to bilayers containing peptide MHC.