Fig. 5.
IL-15-induced DC stimulate a strong T-cell response. Allogeneic T cells (2 × 105) from two donors (a) and (b) were cultured separately for 6 d in a 96-well microtiter plate with mature DC (2 × 102−2 × 105 γ-irradiated cells/well) that were generated either by treating with GM-CSF, IL-4 and TNF-α or IL-15. T-cell proliferation was measured by incorporation of [3H]thymidine. DC without T cells, open symbols (□ and ▵); T cells and DC induced with GM-CSF, IL-4 and TNF-α, ▴; T cells and DC induced with IL-15, ▪. Data were expressed as means of triplicate determinations ± s.e.m. Results are representative of six experiments). Statistical analysis in (a) and (b) shows strong dose effect in each group (P < 0·0001 and P < 0·0004), respectively, but pair wise comparison of two sets at each dose shows no significance differences between IL-15 and GM-CSF, IL-4 and TNF-α induced DC. (c). IL-15-induced DC processed and presented recombinant staphylococcal enterotoxin vaccine (rSEB vaccine) and stimulated vaccine-specific T-cell response. CD14+ monocytes (4 × 105) were cultured with IL-15 for 7 d or with a combination of GM-CSF and IL-4 for 6 d followed by TNF-α for 24 h in the presence or absence of different concentrations of rSEB vaccine (0·03 µm to 3 µm) in a 96-well microtitre plate. After 7 days of culture media were removed, and the wells were washed gently to remove residual cytokines. Cells were cultured with autologous (memory and naïve) T-cells (4 × 105). After day 6 of culture, cells were pulsed with [3H]thymidine for 12 h and proliferation was measured by incorporation of [3H]thymidine. Combination treatment with GM-CSF, IL-4 and TNF-α, ▴; IL-15 treatment, ▪; without cytokine treatment (control), U25CF. Data were expressed as means of triplicate determinations ± s.e.m.