Staging and resetting T cell activation in SMACs


During the productive interaction of T cells with antigen-presenting cells (APCs), engaged receptors, including the T cell antigen receptors and their associated tyrosine kinases, assemble into spatially segregated supramolecular activation clusters (SMACs) at the area of cell contact. Here, we studied intracellular signaling in SMACs by three-dimensional immunofluorescence microscopic localization of CD3, CD45, talin, phosphotyrosine, Lck and phosphorylated ZAP-70 in T cell–APC conjugates. Two distinct phases of spatial-temporal activation, one before and one after SMAC formation, which were separated by a brief state of inactivation caused by CD45, were observed at the T cell–APC contact area. We propose that pre-SMAC signals are sufficient to activate cell adhesion, but not productive T cell responses, which require orchestrated signaling in SMACs.

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Figure 1: Spatial and temporal clustering of talin and pY at the 3D-reconstructed T cell–APC contact site.
Figure 2: Spatial-temporal colocalization and segregation of Lck and CD45 at the 3D-reconstructed T cell–APC contact site.
Figure 3: Spatial-temporal redistribution of CD45 into the dSMAC but not the pSMAC.
Figure 4: Transient recruitment of CD45 to engaged TCRs induced by immobilized peptide–I-Ek tetramers.
Figure 5: Detection of FRET between CD3 and CD45 in the cSMAC.
Figure 6: The spatial-temporal appearance of phosphorylated ZAP-70 in the T cell–APC contact.


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We thank P. Marrack, A. Weiss and G. Koretzky for helpful comments and T. Potter for critical reading of the manuscript. Supported in part by grants from the NIH (to A. K.).

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Correspondence to Abraham Kupfer.

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A. K. is cofounder and co-owner of Intelligent-Imaging Innovations, Inc.

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Freiberg, B., Kupfer, H., Maslanik, W. et al. Staging and resetting T cell activation in SMACs. Nat Immunol 3, 911–917 (2002).

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