Identification and characterization of intestinal Peyer's patch interferon-alpha producing (plasmacytoid) dendritic cells.

Recently, a subset of murine dendritic cells (DC) has been identified that resembles human plasmacytoid (pDC) the principal interferon-alpha (IFN-alpha) producing cells in blood. In this study, C57BL/10 (B10;H2b) mice were treated with fms-like tyrosine 3 kinase Ligand (Flt3L; 10 microg/d; i.p.; 10 days) that expands DC selectively in vivo. Putative pDC (CD11c+B220+) were identified in the subepithelial dome and in interfollicular regions of intestinal Peyer's patches (PP) from both normal and Flt3L-treated animals. Freshly-isolated, immunobead-purified CD11c+ DC from PP were flow-sorted to obtain lineage- (CD11b-CD19-) CD11c+ B220+ DC (purity>96%). Flow cytometric analysis revealed that these sorted PPpDC were negative for surface markers associated with myeloid DC (CD11b) and expressed only low levels of the "lymphoid-related" DC marker CD8alphaalpha+. They expressed low levels of costimulatory molecules and moderate MHC class II. They proved weak stimulators of naïve allogeneic (C3H; H2k) T-cell proliferation. Cytospin preparations of sorted CD11c+B220+ cells revealed plasmacytoid morphology similar to that of human pDC. Immunocytochemistry and enzyme immunoassay revealed that, within 24-hour culture with Herpes simplex virus (10 p.f.u./cell), a subpopulation of stimulated (but not unstimulated) CD11c+B220+ DC produced and secreted IFN-alpha. This novel DC subset may play important roles in innate and adaptive immune responses of the gut and in the regulation of mucosal immune reactions.