IDO activation resulting in immune cell activity modifications. AhR, aryl hydrocarbon receptor; APC, antigen-presenting cell; CTLA4, cytotoxic T-lymphocyte associated protein 4; GCN2, general control non-derepressible 2; IDO, indoleamine 2,3-dioxygenase; IFN-γ, interferon-γ; IL-4, interleukin-4; IL-10, interleukin-10; LPS, lipopolysaccharide; MHC, major histocompatibility complex; mTOR, mammalian target of rapamycin; NK, natural killer; NO, nitric oxide; PD-L1, programmed death-ligand 1; TGF-β, transforming growth factor-β; Th, T helper cell; TLR, toll-like receptor; TNF-α, tumor necrosis factor-α; Treg, regulatory T cell. Created with https://www.BioRender.com (accessed on 1 August 2024).