PDCs and CD11c⁺ DCs produce substantial amounts of IFN-α on incubation with TB40/E, whereas imoDCs do not. PDCs (A), CD11c⁺ DCs (B), and imoDCs (C) were incubated with mock or TB40/E (MOI, 10-20) and were cultured for 84 hours. IFN-α production in the supernatants was measured by ELISA (B; P < .001). Secretion of inflammatory cytokines by PDCs and CD11c⁺ DCs on viral challenge was measured in supernatants by CBA using flow cytometry (D-E). All mean ± SEM are indicated (A, n = 3; B, n = 13; C, n = 5; D, n = 8; E, n = 9; separate donors).