We found that LPS-stimulated mDCs are able to induce up-regulation of co-stimulatory molecules on co-cultured pDCs. Likewise, CpG-stimulated pDCs activate co-cultured mDCs. The cross talk between these two populations of DC is very efficient since it can be observed at mDC/pDC ratio ranging from 1/10 to 10/1.

These DC were matured using CpG-DNA as TLR9 ligand. Mature DCs upregulated CD80, CD86, MHC class II and produced cell type specific cytokines. CD8+ myeloid DCs “cross-presented” exogeneous Ags (Ovalbumin).

We found that CD8alpha- DC produced undetectable levels of IL-12p70 upon stimulation with CpG.

We found that BM-myeloid and splenic CD8alpha+ DC produced at least fivefold less IL-12p70 than plasmacytoid pDC responding to both CpG and the TLR-7 ligand R848.