Although IDO1 is genetically homologous to IDO2, the two enzymes have distinct expression patterns and roles: IDO2 exerting robust pro-inflammatory activity in autoimmune functions acting on B cells, whereas IDO1 is able to mediate the suppression of T cells, in opposition to the functions associated with autoimmunity [80,81,82,83,84]. This evidence concerns the gene IDO1 and Autoimmunity.