Fourth, the inability of an IDO inhibitor to counteract 4-1BB regulatory effects indicate that IDO accumulation in macrophages and dendritic cells - a mechanism which suppress CD4+ T cell responses in experimental uveoretinitis and rheumatoid arthritis through release of IFN-γ by 4-1BB-activated T cells [34], [47] - was not activated by Ag85B-specific CD8+ T cells and was not involved in control of Ag85B-induced IFN-γ response. This evidence concerns the gene IDO1 and rheumatoid arthritis.