This report also reveals key structural requirements for particular germline-encoded residues in mouse MAIT CDR1α (i.e., the TRAV1-2/TRAV1-unique “G-F-N” motif), CDR2α (i.e., the shared TRAV1-2/TRAV1-“V-L” motif), CDR3α (the TRAJ33-exclusive “S-N-Y-Q” motif), and TRBV13-associated residues from CDR2-FWβ, which explains the preferred gene usage of mouse MR1-restricted TRAV1+/TRBV13+ MAIT cells in the context of infection with riboflavin-producing bacteria. The gene discussed is TRAV1-2; the disease is infection.