IL-24 specifically inhibits the phosphorylation of STAT-3 on tyrosine in stimulated GC B cells. (A) Cells (10 × 10⁶ cells/condition) were cultured for 3 days in IL-2 + IL-10 + CD40L and rIL-24 was added thereafter for the indicated time; cells were lysed and submitted to Western blot sequentially revealed after dehybridization, with anti–pY705-STAT-3, anti-STAT-3, anti–pY694-STAT-5, or anti-STAT-5 antibodies. Control was performed in parallel on unstimulated cells. (B) IL-24 transiently reduced STAT-3 phosphorylation. GC B cells from a second tonsil were cultured as in panel A and stimulated with IL-24 for 0.5 and 4 hours before Western blot.