Differential homing mechanisms regulate regionalized effector CD8αβ+ T cell accumulation within the small intestine

H Stenstad, M Svensson, H Cucak… - Proceedings of the …, 2007 - National Acad Sciences
H Stenstad, M Svensson, H Cucak, K Kotarsky, WW Agace
Proceedings of the National Academy of Sciences, 2007National Acad Sciences
The CC chemokine receptor (CCR) 9 is expressed on the majority of small intestinal, but few
colonic, T cells, whereas its ligand CCL25 is constitutively expressed by small intestinal
epithelial cells. As such, CCR9/CCL25 have been proposed to play a central role in
regulating small intestinal but not colonic immune responses and thus to organize
regionalized immunity within the intestinal mucosa. Here, we demonstrate that CCL25 is
expressed at reduced levels by epithelial cells in the distal compared with proximal small …
The CC chemokine receptor (CCR)9 is expressed on the majority of small intestinal, but few colonic, T cells, whereas its ligand CCL25 is constitutively expressed by small intestinal epithelial cells. As such, CCR9/CCL25 have been proposed to play a central role in regulating small intestinal but not colonic immune responses and thus to organize regionalized immunity within the intestinal mucosa. Here, we demonstrate that CCL25 is expressed at reduced levels by epithelial cells in the distal compared with proximal small intestine, which correlated with less efficient CCR9-dependent effector CD8αβ+ T cell entry into the ileal epithelium. In vitro-generated α4β7+ effector CD8αβ+ T cell entry into the lamina propria was less dependent on CCR9 than entry into the epithelium along the entire length of the small intestine and in particular in the ileum. CCR9-independent α4β7+ effector CD8αβ+ T cell entry was pertussis toxin-sensitive, suggesting a role for additional GαI-linked G protein-coupled receptors. Finally, in vivo-primed effector CD8αβ+ T cells displayed regionalized differences in their entry to the small intestinal epithelium with enhanced CCR9-independent entry to the ileum. These results highlight a hitherto underappreciated compartmentalization of immune responses within the small intestine and have direct implications for targeting strategies aimed at regulating T cell localization to the small intestinal mucosa.
National Acad Sciences