In addition to engaging tryptophan metabolism, IDO enhances immunosuppressive factors of the complement immune system. This finding likely explains in part why immunotherapy efforts in incurable cancers such as glioblastoma have fallen flat, according to Derek Wainwright, Ph.D., assistant professor of Neurological Surgery and senior author of the study.

"We have opened up new possibilities into understanding how IDO suppresses the anti-cancer immune response that is independent of its historical and predominant association with tryptophan metabolism," said Wainwright, who is also a professor of Medicine in the Division of Hematology and Oncology and of Microbiology-Immunology.

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