Immunological reagents and uses therefor

An MR1-ligand subunit [MR1-L] which binds MAIT cells, wherein said ligand is represented by Formula (I):

• or a salt, tautomer, or stereoisomer thereof
• wherein:
• R1 is selected from the group consisting of:
• X—C(O)—R1′ (where R1′ is H, or optionally substituted C1-C6alkyl, and X is independently a bond or a divalent linker selected from the group consisting of C1-C3 optionally substituted alkylene, —NR2′— optionally substituted C1-C3alkylene-, —O— optionally substituted C1-C3alkylene-, —S— optionally substituted C1-C3alkylene-, —S(O)— optionally substituted C1-C3alkylene-, —N═CR2′—, —CR2′═CR2″—, —NR2′—C(O)—, —O—C(O)—, or —S—C(O)— where each R2′ and R2″ is independently selected from H, halogen, CN, or optionally substituted C1-C6alkyl);
• —X′—C(O)NR3′R4′ (where R3′ is H or optionally substituted C1-C6alkyl and R4′ is optionally substituted C1-C6alkyl, OH, or CN or R3′R4′ together form an optionally substituted heterocyclyl or optionally substituted heteroaryl, and X′ is independently a bond or a C1-C3 optionally substituted alkylene);
• —X″—C(O)OR5′ (wherein R5′ is H or optionally substituted C1-C6alkyl, and X″ is independently a bond or a C1-C3 optionally substituted alkylene);
• —X′″—C(O)NHSO2R6′ (wherein R6′ is optionally substituted aryl, or optionally substituted C1-C6alkyl, and X′″ is independently a bond or a C1-C3 optionally substituted alkylene);
• and —X″″—S(O)2NHR7′ (wherein R7′ is H, optionally substituted C1-C6alkyl, or optionally substituted aryl, and X″″ is independently a bond or a C1-C3 optionally substituted alkylene);
• R2 is selected from the group consisting of optionally substituted C1-8alkyl, —NH(optionally substituted C1-6alkyl), —N(optionally substituted C1-6alkyl)(optionally substituted aryl), —N(optionally substituted C1-6alkyl)2, —O(optionally substituted C1-6alkyl), —OC(O)(C1-6alkyl), —S(optionally substituted C1-6alkyl), —SC(O)(C1-6alkyl), and —S(O)(optionally substituted C1-6alkyl);
• and
• Y and Z are oxo.