Consistent with previous findings,20 21 this study observed elevated levels of cortisol, IL-6 and IL-1β in the plasma, and increased IDO/TDO ratios in the oral mucosal and colonic tissues of GF-4NQO-CRS mice, indicating that the disrupted oral microbiome drives the biosynthesis of Trp towards Kyn. The gene discussed is TDO2; the disease is congenital rubella syndrome.