c-MPL stimulated sequential killer T cells form more efficient immune synapses. (A) Experimental set up. (B) Representative images of immune synapses between T cells and BV173 leukemia cells. Phase contrast (left) and confocal images (right) at baseline and after coculture. Actin (white), pericentrin (blue), perforin (green). (C) Quantification of the percentage actin at the synapse, the distance of the microtubule organization center to the synapse, and the perforin distance to the synapse. n = 3, mean ± SD. **P ≤ .01; Student t test on log transformed data. NS, not significant.