Figure 1.

Microvilli and Invadosome-like protrusions. (A) Microclusters are accumulations of TCRs found on activated T cells imaged on lipid bilayers or glass. On bilayers, they can move centripetally to form the central supramolecular activation cluster (cSMAC). (B) Microvilli have been imaged using different techniques. Here a method called “quantum dot enabled surface contact mapping” is shown. T cells are placed on a bilayer coated with small (<20 nm), fluorescent quantum dots (Qdots). Microvilli can be observed in TIRF mode (see Box 1) by imaging the displacement of Qdots (“footprints”). (C) Invadosome-like protrusions (ILPs) are observed on T cells placed on a monolayer of endothelial cells (EC). When the membranes of the endothelial cells are imaged, “footprints” of ILPs can be seen as circular areas with decreased membrane dye fluorescence. The dotted line indicates the image plane shown in the right drawing. (D) Using a combination of the techniques described in (A,B) microclusters (MCs) and microvilli (MVs) can be imaged at the same time. Cai et al. (6) found that microclusters and microvilli colocalized on activated T cells. Notably, not all microvilli showed colocalization, however.