The small intestine hosts specialized lymphoid structures, the Peyer's patches, 
that face the gut lumen and are overlaid with unique epithelial cells, called 
microfold (M) cells. M cells are considered to constitute an important route for 
antigen uptake in the mucosal immune system. Here, we used intravital microscopy 
to define immune cell populations, which are in close contact with M cells and 
potentially sample antigen. We present live evidence that DCs enter M cell 
pockets and highlight the abundance of mononuclear phagocytes in these 
structures. Taking advantage of the respective reporter animals, we focused on 
classical DCs that express Zbtb46 and analyzed how these cells interact with M 
cells in steady state and sample antigen for T cell activation in the Peyer's 
patches following challenge.