BL cells were stained with MoAb against CD77 after 72 hours of stimulation with CD40L alone. Additional staining with MoAb against CD77, CD23, and CD40 was performed after 72 hours of stimulation with CD40L in combination with IL-4. FACS analysis was performed after 5 days of culture (including the initial 72 hours of stimulation). Untreated control cells are shown for comparison as a superimposed thin line on each histogram.