DCs elongate in the presence of T cells. (A) Frequency of T cells, DCs, and T cell–free DCs incubated in the presence of T cells plotted as a function of their SF values. Orthogonal projections of T cell were roughly circular (SF = 0.89 ± 0.05; n = 64), whereas those of DCs were elongated (SF = 0.56 ± 0.17; n = 269; P < .001 compared with T cells). In the presence of T cells, DCs become more elongated (SF = 0.51 ± 0.17; n = 379; P = 0.001 relative to DCs alone). (B) SF values determined for individual cells are plotted for each cell type; mean values plus or minus 95% confidence intervals are indicated.