Inosine: novel microbiota-derived immunostimulatory metabolite

In a recent paper published in Science, Mager et al. identify inosine as a metabolite produced by Bifidobacterium pseudolongum that improves the efficacy of anticancer immunotherapy in mice. Inosine produced in the gut reaches adenosine A2A receptors of T lymphocytes infiltrating tumors; thus, inosine joins an expanding list of immunostimulatory metabolites produced in the gut.