Transduced DCs induce a specific cytotoxic response against the Flu peptide in the absence of CD4⁺ T cells and in the absence of exogenous cytokines.

(A,B) Purified HLA A2.1⁺ T cells before and after depletion of CD4⁺ T cells. (A) T cells (gate R, left panel) were purified as described in “Materials and methods” and stained with anti-CD3 and anti-CD19 antibodies (middle panel) or anti-CD8 and anti-CD4 antibodies (right panel). (B) Depletion of CD4⁺ T cells was accomplished as described in “Materials and methods.” After depletion, T cells (gate R, left panel) were stained with the same antibodies (middle and right panels). Background staining given by mouse isotype IgG controls was always lower than 0.25% and subtracted. (C) HLA A2.1⁺ DCs were cultured with autologous CD4-depleted T cells for 8 to 10 days in the absence of exogenous cytokines. CTL assays were performed on T2 cells as described in Figures 5 and 6. The following populations of DCs were compared: DCs pulsed with the Flu peptide (DC⁺), DCs transduced with the HIG vector and pulsed with the Flu peptide (DC.HIG⁺), and DCs transduced with the HFIG vector (DC.HFIG). Without CD4 depletion and using the same absolute number of T cells at the start of the cocultures, cytotoxic activity was comparable to that shown in Figure 5(data not shown).