CXCL9 and infection: This is consistent with the idea that once the majority of T cells have reached the sites of infection, they arrest through a combination of physical confinement (the epithelium is narrow in cross section, and there is dense extracellular matrix underlying the epithelial surface), high CXCL9 and CXCL10 chemokine concentrations at the epithelium, which can contribute to arrest, and presumably engagement with antigen bearing cells in the form of either APC or infected targets.