CCR9 inhibition does not interfere with the development of immune tolerance to oral antigens

► Increasing antigen dose can overcome the reported deficiency of CCR9−/− mice to develop normal immune tolerance to oral antigens. ► The CCR9 antagonist, CCX507, does not affect the ability of mice to develop normal immune tolerance to oral antigens. ► The results obtained in CCR9−/− mice do not necessarily predict the results of pharmacological inhibition of CCR9.