title: Site-specific anti-tumor immunity: differences in DC function, TGF-beta production and numbers of intratumoral Foxp3+ Treg.
abstract: Gliomas localized within the CNS are generally not rejected by the immune system despite being immunogenic. This failure of the immune system has been associated both with glioma-derived immunosuppressive molecules and the immune-privileged state of the CNS. However, the relative contribution of tumor location to the glioma-mediated immunosuppression, as well as the immune mechanisms involved in the failure of glioma rejection are not fully defined. We report here that syngeneic GL261 gliomas growing either intracranially or subcutaneously in mice are infiltrated by DC and T cells. However, only subcutaneous gliomas elicit an effective anti-tumor immune response. In contrast to DC infiltrating subcutaneously grown GL261 gliomas, tumor-infiltrating DC from intracranial gliomas do not activate antigen-dependent T-cell proliferation in vitro. In addition, brain-localized GL261 gliomas are characterized by significantly higher numbers of Foxp3(+) Treg and higher levels of TGF-beta1 mRNA and protein expression when compared with GL261 gliomas in the skin. Our data show that gliomas in the CNS, but not in the skin, give rise to TGF-beta production and accumulation of both Treg and functionally impaired DC. Thus, not the tumor itself, but its location dictates the efficiency of the anti-tumor immune response.
authors.affiliation: Division of Clinical Immunology, University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Gregoire
authors.initials: G
authors.lastname: Biollaz
authors.forename: Luca
authors.initials: L
authors.lastname: Bernasconi
authors.forename: Christine
authors.initials: C
authors.lastname: Cretton
authors.forename: Ursula
authors.initials: U
authors.lastname: Püntener
authors.forename: Karl
authors.initials: K
authors.lastname: Frei
authors.forename: Adriano
authors.initials: A
authors.lastname: Fontana
authors.forename: Tobias
authors.initials: T
authors.lastname: Suter