Polarization of naive T cells into T_H1 or T_H2 effectors by CD40L-activated BCP-ALL cells. After 1 day of culture, BCP-ALL cells were activated (or not) by CD40 ligation. Cytokine production by purified cord blood T lymphocytes after coculture with BCP-ALL cells (□) or CD40L-activated BCP-ALL cells (▪) was assessed by intracellular staining of IL-4 (A) and IFN-γ (B) with specific mAb after cell permeabilization. Data are expressed as the percentage of cytokine-producing cells. Normal DCs were differentiated from monocytes in the presence of GM-CSF + IL-13. Data from normal DCs refer to mean ± SD of 3 different experiments.