Fig. 4. Induction of IκBα expression is not required for repression of NF-κB activity in MEFs and CD4⁺ splenocytes. (A) GR^+/+ and GR^dim MEFs were treated with 10^–7 M dexamethasone for 2 h followed by treatment with 50 ng/ml TNF-α. IκBα protein content was measured by immunoblotting. (B) CD4⁺ splenocytes from NF-κB transgenic reporter mice expressing either wild-type (GR^+/+) or DNA binding-defective GR (GR^dim) were cultured on αCD3-coated culture dishes in the absence or presence of 10^–6 M dexamethasone for 4 h. Expression of the reporter gene (B) was determined by RNase protection analysis and normalized to CytOX. Relative IκBα mRNA levels (C) were determined by northern blot analysis and IκBα protein (D) was detected by western blot analysis.