MR1Ts, of which MAIT cells are a subset, are considered to be innate based upon their usage of the highly conserved molecule MR1, and on the dependence of the semi-invariant TCR alpha chain TRAV1-2. In humans, this high degree of conservation is acquired shortly after birth. It is also increasingly clear that MR1T TCRs are surprisingly diverse with regard to beta chain usage, and that this diversity is associated with the ability to distinguish different MR1 ligands. Here, we explore MR1Ts, defined based on an MR1-tetramer, in the lungs and peripheral circulation in household contacts of subjects exposed to Mycobacterium tuberculosis, and where immunologic assessment, microbiologic assessment, and imaging using PET/CT can be used to define the full spectrum of outcomes following exposure.