A subset of naive CD8+ T cells recognizing antigen (Ag) in GALT, but not PLNs, selectively retains CCR9 expression and is targeted to the small intestinal epithelium (4). Selective expression of adhesion molecules such as α4β7 and αEβ7 are also likely to contribute to this tropism (18). Within the small intestine, CCL25 produced by IE mediates homing of effector CD8+ T cells by promoting rapid adhesion, diapedesis, and/or entry of cells into the IE (8).
