KLRB1 and tuberculosis: In BAL fluid obtained from patients with TB, TRAV1-2+ CD8+ T cells expressed low levels of CD161 compared with peripheral blood TRAV1-2+ CD8+ T cells (Fig. 3d), which is consistent with the data from healthy lung tissue (Fig. 1c) and the prior demonstration that CD161 can be down-regulated as a result of MAIT cell activation17,28,29.