Figure 3.
(a) Up‐regulation of CD23 and CD80 as a consequence of CD154/wt or CD154/G219R signalling. Shown are two‐colour histograms of Ramos B cells stimulated with mock transfected or 293 cells transiently transfected with either CD154/G219R or CD154/wt. Cocultures were established with a B cell to stimulator cell ratio of 4 : 1 for 24 hr prior to staining with biotin‐conjugated anti‐CD20 mAb, followed by streptavidin–PE and FITC‐conjugated anti‐CD23 mAb or FITC‐conjugated anti‐CD80 mAb. Numbers in the upper right hand quadrant of each histogram refer to the percentage of CD20 cells that are also positive for CD23 or CD80 expression. (b). Effects of CD154/wt and CD154/G219R signalling on Iγ transcription. Ramos B cells (5 × 105) were incubated for 2 days with an equal number of 293 cells transiently transfected, 293/G219R, or 293/wt in the presence or absence of IL‐4. B cells were assayed for Iγ expression by RT–PCR using Iγ‐ and Cγ‐specific primers that recognize Iγ transcripts of all subclasses and hybridization to a γ1‐specific hinge probe (arrows in schematic drawing indicate approximate location of PCR primers). Shown is the expression of Iγ1 transcripts isolated from Ramos B cells incubated under the following conditions: Lane 1, 293 cells; Lane 2, 293 + IL‐4; Lane 3, 293/G219R cells; Lane 4, 293/G219R + IL‐4; Lane 5, 293/wt; Lane 6, 293/wt + IL‐4.