The expression and function of murine FcgammaR in these CD11c+CD11b-B220+ plasmacytoid DCs was investigated.

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. Matured pDCs pDCs produced type 1 Interferons.

We examined whether plasmacytoid pDC are infected and/or activated by MTb, and whether they play a role in regulating bacterial clearance during acute MTb infection and if so how. We have compared these DC with myeloid DC and macrophages with respect to MTb infection.

These plasmacytoid pDC that were stimulated with both CpG and the TLR-7 ligand R848 were shown to produce very high levels of IL-12p70 (in the ng/ml range per 5 x 105 cells/ml) and IFN-gamma.