T-cell function after drug-intake shows different dynamics after conversion from cyclosporine A to tacrolimus. (A) Dot plots above show SEB-stimulated CD4 T-cells producing IL-2 (upper left quadrant) or IFN-γ (lower right quadrant) or both cytokines (upper right quadrant) before (8:00 a.m.) and after (10:00 a.m. and 12:00 p.m.) intake of cyclosporine A (upper panel) or tacrolimus (lower panel). Percentages of reactive CD4 T-cells are indicated in the corresponding quadrants. Kinetics of SEB-reactive T-cells producing the cytokine IFN-γ (circles, corresponding to cells in the two upper quadrants) and IL-2 (squares, corresponding to cells in the two right quadrants) at 8:00 a.m., 10:00 a.m. and 12:00 p.m. under cyclosporine A and after conversion to tacrolimus are shown in panel (B). Corresponding drug-levels are indicated.