CCR6 and tuberculosis: This conjecture is based on the fact that IL-22–producing cells have been detected in the lungs and granulomas of rhesus monkeys with TB (43, 44), that soluble IL-22 has been found to be elevated at the site of disease during both pulmonary and extrapulmonary TB (24, 25), and also that IL-22–producing cells express CCR6, which has been shown to mediate T cell homing to mucosal tissues (31).