However, mouse genetic studies support a link between indoximod action and IDO2 function, for example, in demonstrating that the therapeutic benefits of indoximod administration in a model of rheumatoid arthritis that relies on the presence of the Ido2 gene (74), which interacts genetically with IDO1 in IDO1-mediated activation of Treg cells in the mouse (28). This evidence concerns the gene IDO2 and rheumatoid arthritis.