MR1 is a unique antigen presenting molecule that presents microbial metabolites to MR1-restricted T cells. The exact mechanisms by which MR1 captures antigens from intracellular microbes remains unclear. We have shown that endosomal trafficking is important for MR1-dependent presentation of Mycobacterium tuberculosis (Mtb). In our follow-up studies, we have found a unique role for endosomal calcium channels and calcium-sensitive trafficking proteins in the presentation of Mtb-derived antigens.