Figure 4.

The effects of D–Lc on CD40-activated B cell are restricted to CD1a⁺ dendritic cells and are not due to potentially contaminating T cells. (A) In vitro generated D–Lc were FACS^® sorted into CD1a⁻ cells and CD1a⁺ DC and used as stimulators of 10⁴ CD40-activated B cells. Increasing numbers of either total D–Lc or FACS^® sorted populations were added to the culture to study (a) the cytokine-independent proliferation of B cells, (b) the cytokineindependent IgG production, and (c) the IL-2-dependent IgM production. Results are expressed as mean of triplicate cultures (SD ⩽ 10%). (results from 1 experiment representative of 3). No significant B cell proliferation and differentiation was observed in absence of CD40L L cells. (B) The phenotype of cultures consisting of total B cells, D–Lc, CD40L L cells, and IL-2 was routinely followed during the culture period. Fluorescence histograms gated on small cells have been obtained with FITC–anti-CD3 and anti-CD19 after exclusion of dead cells using propidium iodide. High FSC/SSC cells correspond to the D–Lc population.