IDO1 is a heme-containing enzyme crucial in tryptophan metabolism and immune regulation. It breaks down L-tryptophan into kynurenine through a complex oxygen-dependent process.

Key functions include:

• Immune system modulation
• Maintaining immune tolerance
• Suppressing immune responses

Mechanism of immune suppression:

• Reduces tryptophan levels
• Increases kynurenine metabolites
• Triggers T cell dysfunction
• Promotes regulatory T cell development

Pathological implications:

• Cancer: Tumors exploit IDO1 to evade immune detection
• Autoimmune diseases: IDO1 dysfunction can trigger immune reactions
• Chronic infections: Altered IDO1 expression impacts immune function

In pregnancy, IDO1 helps prevent fetal rejection by fostering immune tolerance.

Therapeutic approaches:

• Developing IDO1 inhibitors
• Targeting cancer treatment
• Exploring potential in: Autoimmune diseases, Chronic infections, Transplant medicine

Challenges:

• Optimizing inhibitor effectiveness
• Identifying optimal patient groups
• Balancing immune suppression and activation

Current research focuses on:

• Precise inhibitor development
• Combination treatment strategies
• Understanding IDO1's signalling pathways