In addition to these hallmarks of tolerogenic DCs, the secretion of IL-2 and a variety of enzymes such as retinaldehyde dehydrogenase-2 and indolamine 2,3 dioxygenase are involved in the suppression of Th1-mediated autoimmunity in addition to the induction of Treg cells [46–48]. The gene discussed is IDO1; the disease is Autoimmunity.