Effect of retinoic acid on the expression of various cell cycle regulatory proteins in human B cells. (A) Mitogenic stimulation and retinoic acid treatment of the cells were performed as described in the legend to Fig 3B. Total cell lysates were prepared and equal amounts of total protein (60 μg) were subjected to Western blot analysis with antibodies against the proteins indicated on the right. (B) Cells (1.5 × 106 cells/mL) were stimulated for 16 or 24 hours before addition of retinoic acid (1000 nmol/L). The cells were then treated with retinoic acid for the indicated times and analyzed for the expression of p21Cip1 by Western blot analysis. μ, F(ab′)2 fragment of rabbit antihuman IgM; SAC, Staphylococcus aureus crude cell suspension; RA, retinoic acid.
