Downregulation of PP2Ac restores IL-2 production and IL2 promoter activity in SLE T cells. (A) T cells were transfected with either PP2Ac- or control siRNA. Cells were then stimulated with PMA/A23187 for 3 hours. IL-2 was measured as described in Methods. *P = 0.03 and 0.05 when compared with nontransfected normal T cells and with transfected lupus T cells, respectively; **P = 0.05 compared with nontransfected normal T cells. (B) PP2Ac-siRNA treatment downregulates PP2Ac but not PP2Aa expression. Results from 2 independent experiments with normal T cells are shown (PP2Ac/PP2Aa ratios are noted below the panels). (C) T cells were treated as indicated, and IL-2 was measured. Results from 1 of 2 similar experiments are shown. (D) T cells were transfected with plasmids encoding either the wild-type PP2Ac or DN PP2Ac mutants (H118N or L199P). Twenty hours following transfection, cells were stimulated with PMA/A23187 for 6 hours. P values represent the result of paired t test analysis. (E) Results from the same experiment as shown in D, except that T cells were stimulated with OKT3/anti-CD3 mAbs for 18 hours. (F) T cells were cotransfected with (a) a plasmid encoding an IL2 promoter luciferase construct or an empty vector, (b) a β-galactosidase plasmid, and (c) either PP2Ac- or control siRNA. Following 24 hours of culture, cells were stimulated for 1 hour with PMA/A23187. IL2 promoter activity was assessed as the luciferase activity. Numbers show the fold increase in IL2 promoter activity when compared with stimulated cells in the absence of PP2Ac-siRNA. Results from 1 of 2 similar experiments are presented.