DC–IFN- and DC–IFN-β have a decreased capacity to support naive CD4⁺ T-cell proliferation.

Naive CD4⁺ T cells were stimulated with immobilized anti-CD3 and either DC, DC–IFN-α (A), or DC–IFN-β (B) at the indicated ratios. IFN-α and IFN-β were added at indicated concentrations at days 1 and 4 of the culture. APC were washed to remove cytokines used for in vitro differentiation. No exogenous cytokines were added to the cultures for measurement of [³H]-thymidine incorporation. After 3 days in culture, wells were pulsed with 1 μCi of [³H]-thymidine per well. Twenty-four hours later, plates were harvested and incorporated [³H]-thymidine was measured. DC-induced T-cell proliferation was significantly different from DC–IFN-β–induced and DC–IFN-α–induced T-cell proliferation at a 1:0.1 ratio (n = 4; P < .05 as determined by a paired t test). Results depicted are representative of 4 independent experiments. (C) Naive CD4⁺ T-cell proliferation induced by DC–IFN-β (1 ng/mL) was not dependent on CD80 costimulation. Anti-CD80 and anti-CD86 were added at the beginning of the proliferative assays at a final concentration of 10 μg/mL. Data are expressed as the percentage of inhibition of proliferation in the presence of isotype-matched control Ig at a T-cell to DC ratio of 1:0.1. Results shown are the mean and SEM of 3 independent experiments.