Proliferative responses of naive allogeneic T cells to DC1 and DC2.

DC1 and DC2 from normal (A, B) or G-CSF-treated (C, D) donors were purified as shown in Figure 3. Purified DC were used as stimulators either fresh (A, C) or after 48 hours pre-activation in vitro by GM-CSF, IL-3, and TNF-α (B, D). Unfractionated PBMC were used as control stimulators. CD4⁺/CD45RA⁺ naive T cells were purified by immunomagnetic beads, as described in “Materials and methods.” Autologous or allogeneic, purified CD4+/CD45RA+ T cells were used as responders in a 6-day culture assay. T-cell proliferation was measured by ³H]TdR incorporation. Proliferation of autologous T cells was always less than 500 cpm when cocultured with fresh DC (n = 2) and less than 2000 cpm when cocultured with activated DC (n = 3).