I just came across a rather nifty paper published in PNAS a couple of weeks back.

Micropatterning of costimulatory ligands enhances CD4 T cell function
Shen et al, PNAS (2008) 105: 7791–7796; www.pnas.org/cgi/doi/10.1073/pnas.0710295105

The 'bullseye' pattern of the immunological synapse that drives cell activation, with supra molecular activation clusters in rafts (SMACs) has been known for some time now. However,  there was no direct evidence that T cells recognize and respond to micrometer-scale organization of CD28 ligands, especially with respect to TCR signaling complexes. To address this issue, these authors replaced the APC with a planar substrate cont aining high-density arrays of antigenic and costimulatory signals, and ended up with some cool videos, images and signaling information that demonstrates how the 'peripheral' presentation of CD28, a key costimulatory receptor, affects T cell activation and IL-2 production.

Check out the supplementary data / videos too: the slow scanning as the cells try to get to the optimal 'pattern' is cool. (the movies load very slowly - don't know if that has something to do with the PNAS website).