Vitamin B2 (riboflavin) is essential for metabolic functions and is synthesized by many
bacteria, yeast, and plants, but not by mammals and other animals, which must acquire it
from the diet. In mammals, modified pyrimidine intermediates from the microbial biosynthesis
of riboflavin are recognized as signature biomarkers of microbial infection. This recognition
occurs by specialized lymphocytes known as mucosal associated invariant T (MAIT) cells.
The major histocompatibility class I-like antigen-presenting molecule, MR1, captures these …