MPs can sample luminal antigens which traverse microfold (M) cells located within the FAE. These antigens are then presented in the T cell zone. However, it is unclear how M cells and MPs cooperate as they sample antigen. It is also unclear whether the antigen is presented to T cells by the MPs that initially sampled it, or transferred to DCs found in the T cell zone.
Using two-photon microscopy in live transgenic mice, we investigated the interactions between M cells, MPs and T cells in the PP. We began to investigate the interaction between MPs and M cells, capturing previously-unobserved behavior of MPs as they migrate within the epithelium, enter into microfolds and interact with M cells. Antigen uptake and T cell activation by MPs was assessed following administration of fluorescent antigens. MPs accumulated and presented particulate antigen in vitro, resulting in T cell proliferation. Particles injected to the intestines accumulated in MPs in the PP. Administration of soluble antigen activated T cells, which formed dynamic clusters in the T cell zones and upregulated CD69. These results present our abilities to follow MPs as they interact with M cells and T cells as they are activated within the PP.