5-A-RU (5-Amino-6-(D-ribitylamino)uracil) is an early intermediate in riboflavin biosynthesis and is found in a variety of bacteria and yeast as well as plants. 5-A-RU is also a mucosal-associated invariant T (MAIT) cell activator that forms potent MAIT-activating antigens through non-enzymatic reactions with small molecules from other metabolic pathways.

METHODS: 5-A-RU plus DHA, 5-A-RU, 5-A-RU plus MeG, or 5-A-RU (0-3000μM) was used to treat mouse MAIT cells from STg (iVα19) and DTg (iVα19Vβ6) animals, and the activation of mouse MAIT cells was measured.
RESULTS 5-A-RU plus MeG achieved the greatest MAIT cell activation; 5-A-RU alone also activated MAIT cells; 5-A-RU can also react with Glyx and MeG to produce pyrimidine adducts, activating mouse MAIT cells. [2]

METHODS: 5-A-RU (100 nM, intraperitoneal injection) was administered to Vβ6-Tg mice and iVα19-Tg mice, and MAIT cell activation was measured.
RESULTS MAIT cells were activated when 5-A-RU and MeG were mixed extemporaneously before in vivo injection, whereas 5-A-RU alone was unable to activate MAIT cells in mice. [2]