Veto activity of ex vivo–expanded CD34⁺cells: effect on intracellular staining of IFN-γ in the effector T cells.

Responder cells and irradiated allogeneic stimulator cells were cocultured for 5 days in the absence (A and C) and presence (B and D) of cells obtained after a 12-day ex vivo expansion of CD34⁺ cells. The stimulator cells in the MLR (carried out at a veto-to-responder cell ratio of 0.125) were from either the donor of the CD34⁺ cells (A and B) or a third party (C and D). After the 5-day MLR, the cells were subjected to an additional 7-day limiting-dilution culture. The cells were then incubated with phorbol 12-myristate 13-acetate, ionomycin, and monensin; fixed; and stained for detection of the intracellular IFN-γ. Lymphocytes were gated on the basis of their forward scatter–side scatter profile. The percentage of each cell subpopulation is indicated in the relevant area of each dot plot. Shown are data from 1 of 3 experiments.