Subversion of kynurenine-induced AHR activation in CD8 T cells by kynureninase-expressing antigen presenting cells

ABSTRACT: Kynurenine, an intermediate metabolite of tryptophan metabolism, suppresses the antitumor activity of CD8+ T cells by activating the aryl hydrocarbon receptor (AHR). Its role in adaptive immunity is poorly understood. Outside the liver, kynurenine is mainly produced by indoleamine 2,3-dioxygenase 1 (IDO1) and further degraded by kynureninase (KYNU). This report shows that KYNU is predominantly expressed in human and mouse antigen-presenting cells (APCs) in vivo, GM-CSF-differentiated macrophages and dendritic cells in vitro, and alveolar macrophages collected in situ, and is functionally active in breaking down kynurenine into catabolic products without contributing towards de novo NAD+ synthesis. Importantly, while CD8+ T cells uptake kynurenine, they lack active KYNU, leading to AHR-dependent immunosuppression. However, KYNU-expressing APCs can deplete extracellular kynurenine, prevent AHR activation, and restore IFNγ production in CD8+ T cells. This highlights the importance of KYNU-expressing APCs in combating kynurenine-induced immune suppression against tumors.

INSTRUMENT(S):

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Bone Marrow, Macrophage

SUBMITTER: J Patrick Murphy  

LAB HEAD: J Patrick Murphy

PROVIDER: PXD074605 | Pride | 2026-02-23

REPOSITORIES: Pride