FTI treatment does not interfere with CD3/CD28-induced MAP kinase activation. Th1 and Th2 T cells were preincubated with 10 μM of FTI CP 390392 or culture medium for 24 hours, followed by stimulation with beads coated with anti-CD3 (2C11, 1 μg/mL) with or without anti-CD28 (PV1, 1 μg/mL) antibodies. The FTI was present during the whole culture period. 2.5 × 10⁶ cells were used in each experimental condition. After 20 minutes of stimulation, T-cell activation was stopped by placing the cells on ice, and cell lysates were analyzed by SDS-PAGE for the presence of phospho-ERK and phospho-JNK. Total ERK and JNK were assessed as a loading control.