Interestingly, CD8+CD26hi T cells enriched with MAIT cells also significantly reduce in CLL patients, and show a propensity to highly express cytotoxic molecules when stimulated with cytokines rather than CD3/CD28-dependent stimulation, indicating MR1 recognizing CLL-derived ligand is remiss but potentially important for MAIT cell activation in this cancer context. Here, MR1 is linked to B-cell chronic lymphocytic leukemia.