Figure 1: Small intestine and colon homing of lymphocytes.
Antigens in the intestine are captured and processed by intestinal mononuclear phagocytes (MP), which include macrophages and DCs. DCs that have taken up antigen then up-regulate CCR7 expression, which directs their migration to the MLN where they induce differentiation of naive T cells (TN) into regulatory or effector T cells (TE), and imprint them with trafficking receptors that direct them to intestinal mucosa. Localization of T and B cells to the small intestine (left) is mediated by a4b7 (which binds the vascular addressin MADCAM1) and CCR9. Expression of CCR10 together with a4b7 targets plasmablasts to the large intestine.
Citation for figure 1: Gastroenterology. 2016 Feb;150(2):340-54.