MR1 and infection: Several authors have shown that MR1-antigen tetramer+ T cells are not all MAIT cells (10, 61) and contain 1–4% Vα7.2− T cells, one subset of which detects infection with the riboflavin auxotroph Streptococcus pyogenes (S. pyogenes) in a TCR-dependent manner (61), implying that MR1 can present different ligands to MR1-antigen tetramer+ T cells depending on the TCRα chain usage.