CD25 surface expression in PKCθ^–/– and T-cell activation in PKCα^–/– T cells is not affected by PDE4 LMWI. (A-B) Flow cytometric analysis of expression of CD25 wild-type PKCθ^+/+ and PKCθ^–/– T cells. Single-cell suspensions of purified mature CD3⁺ T cells, stimulated or not for 16 hours with anti-CD3 and anti-CD28, were stained with anti-CD25. Percentages of positive cells are indicated. Experiments were repeated at least 3 times with similar results. (C-D) IL-2 production of purified mature CD3⁺ T cells in the presence of inhibitors as specified. Cells were left unstimulated or were stimulated with anti-CD3 (precoated at a concentration of 10 μg mL^–1) plus soluble anti-CD28 (1 μg mL^–1) or PDBu/ionomycin, as indicated. Results shown are the mean ± SD of at least 3 independent experiments. (D, inset) Western blot of CD3⁺ T-cell lysates immunostained for the endogenous PKCα isotype and fyn, as indicated.