Fas internalization in mature DCs treated with anti-CD40. (A) LPS-matured DCs activated for various times with anti-CD40 (B-B20) were stained for cell-surface Fas or HLA-DR expression before confocal microscopy. Images were pseudocolored after acquisition. Blue indicates negative staining and yellow strong staining. HLA-DR was used as a cell-surface control molecule. (B) LPS-matured DCs activated with anti-CD40 isotype control were stained for Fas, as described. (C) To control Fas internalization, LPS-matured DCs were activated for 2 hours with anti-CD40 at 4°C to block endocytosis. (D) Immature DCs were activated with anti-CD40 and processed as described.