Decreased lipid packing is concomitant with and dependent on cell shrinkage. (A) Lymphocytes from NOD mice were stained with anti-CD19 antibody, preincubated with 0.05 μM MC540, and stimulated with 2 μM calcimycin (arrows) alone (red lines) or together with 10 μM clotrimazole (blue lines). Plots show (Ai) cell shrinkage (decrease in forward light scatter [FSC]), (Aii) percentage of MC540^hi cells, and (Aiii) membrane buckling (side light scatter, [SSC]) plotted as a function of time. (B) Lymphocytes from NOD mice were stained with anti-CD19 antibody. (Bi) Cells were preincubated with AV^FITC alone (left panel) or together with 1 μM tamoxifen (right panel) and stimulated with 2 μM calcimycin (arrows). Density plots show the change in AV binding as a function of time. (Bii) Cells were preincubated with 0.05 μM MC540 and stimulated with 2 μM calcimycin (arrows) alone (red lines) or in the presence of 1 μM tamoxifen (added immediately before baseline recording; blue lines). Plots show cell shrinkage (left panel; decrease in forward light scatter [FSC]); mean MC540 fluorescence units (center panel), membrane buckling (right panel; side light scatter [SSC]); all plotted as a function of time.