Complete blockade of Th1 IFN-γ response in c-Rel–deficient mice. Normal (black bars) and c-Rel^–/– (white bars) mice were treated as in Figure 1a and sacrificed 36 days after immunization. Splenocytes (7.5 × 10⁵/ml) were cultured in complete DMEM with or without 5–25 μg/ml of MOG38-50 peptide. Culture supernatants were collected 40 hours later and tested for cytokines by ELISA. For proliferation assays, cells were pulsed with ³H-thymidine at 48 hours and radioactivity was determined 16 hours later. Results are shown as mean + SD from a total of 12 mice (6 mice per group). The differences between the two groups are statistically significant for all parameters (P < 0.01). The experiments were repeated twice with similar results.