Infection of DCs from the Sub-epithelial Dome Region of Ileal Peyer's Patches with B. abortus

(A) Cellular organization of a Peyer's patch dome. DCs are enriched in the Sub-Epithelial Dome (SED) underlying the Follicle-Associated Epithelium (FAE) and in the Inter-Follicular Region (IFR) in vicinity of the High Endothelial Venules (HEV).

(B) Sixty minutes after intestinal loop infection, B. abortus (red) adhered on both villi epithelium (VE) and FAE surfaces. However, only few of them were observed in villi lamina propria (LP). These were always observed in association with CD11c+ cells (green, arrowhead). Most B. abortus bacteria reached the under-epithelial compartment of the gut through the FAE. Some of these were observed inside CD11c+ cells (arrows and insert), while others were in close association with CD11c+ dendrites (arrowheads).

(C) High magnification field of a Peyer's patch infected with GFP-expressing Brucella. Images in the first and the second row, corresponding to area depicted by the squared box in (A), show either Brucella (GFP in green and LPS in red) internalized by CD11+ cells (blue, representative of 29 out of 118 B. abortus-associated cells) or the close association of one B. abortus expressing GFP with dendrites from a CD11c+ cell of the SED region (representative of 30 out of 118 B. abortus-associated cells), respectively. The image in the last row shows one of the rare B. abortus-associated cells (all CD11c+) from the villus (GC, goblet cells). Close association or internalization was always confirmed by the combined xy, xz, and/or yz views as shown in inserts. Bars, 20 μm.