Introduction of p38α^Y323F mutation into Gadd45αKO mice abolishes the spontaneous development of autoimmunity. (A) T cells from mice of the indicated genotypes were stimulated with plate-bound α-CD3 (5 μg/mL) and α-CD28 (2 μg/mL), and [³H]thymidine was added to the cultures 16 hours before the cells were harvested at the indicated time points (n = 3). (B) T cells were stimulated with α-CD28 (2 μg/mL) and various amounts of α-CD3 for 48 hours, and proliferation was assessed by [³H]thymidine incorporation (n = 2). (C) WT, Gadd45αKO (GKO), and GKO/p38α^Y323F mice were bled at 6, 9, 12, and 15 months of age, and the serum was assayed for antihistone (left panel) or anti-dsDNA (right panel) antibodies. Each point represents mean ± SEM; n = 15. (D) Serum obtained from mice at 12 months of age was assayed for the presence of IFN-α by enzyme-linked immunosorbent assay. P values were calculated by t test; n = 15. (E) Twelve-month-old mice were screened for the presence of proteinuria. The data represent the mean ± SEM; n = 15. P value was determined by t test. N.S. indicates not significant.