AHR and glioblastoma: In vitro activation of bone marrow-derived macrophages (BMDMs) with kynurenine reduced their expressions of MHC Class I and II, as well as the co-stimulatory molecule, CD86, suggesting an immunosuppressive effect.31 In an in vivo glioblastoma model induced by GL261 intracranial injection, the kynurenine produced by glioblastoma cells was found to activate AHR in macrophages, leading to increased expression of CD39.