Oral immunization induces a novel CXCR6+β7+ intraepithelial lymphocyte subset predominating in the small intestine

Intestinal T cells form a central part of the front-line defence against foreign organisms and need to be situated in the mucosa where infection occurs. It is well accepted that immunization by a mucosal route favours localization of antigen-specific effector T cells in the mucosal epithelium, while systemic immunization does not. The aim of the study is to determine how homing receptors are specifically involved in retaining effector T cells in the small intestine after oral immunization. We here demonstrate that the chemokine receptor CXCR6, integrins beta 7 and CD29 contribute differentially to the epithelial retention phenotype of CD8(+) T cells in the small intestine of mice. CD8(+) intraepithelial lymphocytes (IELs) of unvaccinated mice are predominantly beta 7 single positives, and subcutaneous immunization-induced antigen-specific CD8(+) effector IELs are mainly composed of CXCR6(+), CD29(+) and CXCR6(+)CD29(+) cells. Strikingly, the majority of oral immunization-induced antigen-specific CD8(+) effector IELs exhibit a distinct, tissue-specific CXCR6(+)beta 7(+) double-positive phenotype, cytotoxic potential and enhanced intraepithelial localization. Transfer of antigen-specific CD8(+) T cells preactivated with certain immuno-stimuli (such as monophosphoryl lipid A) results in increased accumulation of donor IELs with the CXCR6(+)beta 7(+) phenotype. As beta 7 exclusively paired with alpha E on IELs, our results strongly suggest that CXCR6 may cooperate with the heterodimer alpha E beta 7 to preferentially retain intestinally induced effector IELs in the epithelium. The identification of this novel IEL phenotype has significant implications for the development of vaccines and therapeutic strategies to enhance gut immunity.

Automated summary

The study aims to determine the specific involvement of homing receptors in retaining effector T cells in the small intestine after oral immunization. The results demonstrate that CXCR6 chemokine receptor, integrins beta 7, and CD29 play differential roles in the epithelial retention phenotype of CD8(+) T cells in the small intestine of mice.