Fig. 8. CD82 concentrates in the IS upon contact with APCs. T8-1 cells expressing YFP-tagged CD82 (YFP-CD82) and labeled with the calcium indicator Fura 2 were added to antigen-pulsed L625.7 fibroblasts. (A) Merged phase-contrast images and YFP fluorescence at the beginning of the experiment. Cell 1, uniformly stained, did not move; cell 2 moved rapidly as indicated by the arrow. (B) Merged images of phase-contrast microscopy and either Fura-2-fluorescence ratio (left; low calcium concentration is indicated in blue and high calcium concentration in red) or YFP fluorescence (right) after 20 minutes of contact between T cells and APCs. In T cells with a high intracellular calcium level (1-4), CD82 is relocalized to the T-cell/APC contact area. (C) After 20 minutes of contact with APCs, cells were fixed, permeabilized and labeled with rhodamine-phalloidin. Cells were analysed simultaneously for YFP and rhodamine fluorescence and phase-contrast microscopy. The phase-contrast image is merged with YFP fluorescence (left), rhodamine fluorescence (middle) or both (right).