Figure 3.

The number of CD154 molecules per B lymphocyte influenced the evolution of CD19⁺ CD27^– and CD19⁺ CD27⁺ populations. CD19-purified B lymphocytes were stimulated in the presence of cytokines, and irradiated L4.5^low or L4.5^high cells were adjusted to obtain 1000, 2000, 5000 (L4.5^low), 10 000 and 25 000 (L4.5^high) CD154 molecules per B lymphocyte. In all cases, the number of B cells varied from 2 to 10 per L4.5 cell (L4.5^high or L4.5^low). The expression of CD19 and CD27 was determined on days 5 and 8 as described in Fig. 1. On day 8, ellipsoid regions highlight three distinct populations, namely CD19⁺⁺ CD27^–, CD19^low CD27^– and CD19⁺ CD27⁺⁺. For day 5 data, numbers indicate the percentages of cells in the indicated quadrants, whereas for day 8 data, they refer to the percentages of cells in each region. These results are representative of three independent experiments.