DC cross-talk depends on TNF-α, IFN-α, and cell contact. (A) The percentage of CD40⁺ pDCs and mDCs was determined after mDC/pDC coculture, as in Figure 1. The effects of LPS treatment with or without neutralizing anti-TNF-α mAbs (right panel) or CpG stimulation in the presence or absence of neutralizing anti-type I interferon receptor mAbs (left panel) were determined for pDCs and mDCs, respectively. (B) CD40 expression by pDCs treated with TNF-α (right panel) or mDCs treated with IFN-α (left panel) is compared for mDCs and pDCs cultured alone (■) or in coculture (). (C) pDCs were treated with supernatants from mDCs cultured alone or with pDCs after LPS stimulation, and CD40 expression was determined (right panel). Similarly, mDCs were treated with supernatants from pDCs alone or in coculture that was treated with CpG (left panel). (D) The percentage of CD40⁺ pDCs (right panel) and mDCs (left panel) after culture in isolation without stimulation (□) and stimulated together either in the same well (■) or separated by a semipermeable membrane (). As before, LPS (right panel) or CpG (left panel) was used as mDC- or pDC-selective stimuli. All experiments in this figure are representative of 3 performed.