MR1 and tuberculosis: Because BCG is a weaker MAIT cell activator than M. tuberculosis (as shown in this study) and other bacteria such as Francisella tularensis LVS (88), and because BCG vaccination activates MAIT cells mainly via an MR1-TCR signaling-independent mechanism (39), we hypothesized that a recombinant BCG which overexpresses MAIT cell ligands might show enhanced protection against TB via improved MR1-TCR signaling-dependent MAIT cell activation and MR1-TCR-independent innate and adaptive immunity generated in response to antigens of BCG.