MR1 and cancer: We demonstrated that our TCRs reacted to breast cancer cells but not to the other cancer cells nor normal breast tissue cells, while MR1 T cells reported by Crowther et al. reacted to various tumor cell lines [12], and MR1 T cells reported by Lepore et al. reacted not only to MR1-expressing leukemia cells but also MR1-expressing melanoma cells [11].