ABSTRACT Multiple Sclerosis (MS) is a chronic, inflammatory disease of the central nervous system. Despite the pharmacological arsenal approved for MS, there are treatment-reluctant patients for whom cell therapy appears as the only therapeutic alternative. Myeloid-derived suppressor cells (MDSCs) are immature cells of the innate immune response able to immunosuppress T lymphocytes and to promote oligodendroglial differentiation in experimental autoimmune encephalomyelitis (EAE), a preclinical model for MS. Culture devices need to be designed so that MDSCs maintain a state of immaturity and immunosuppressive function similar to that exerted in the donor organism. Graphene oxide (GO) has been described as a biocompatible material with the capacity to biologically modulate different cell types, including immune cells. In the present work, we show how MDSCs isolated from immune organs of EAE mice maintain an immature phenotype and highly immunosuppressive activity on T lymphocytes after being cultured on 2D reduced GO films (rGO 200 ) compared to those grown on glass. This activity is depleted when MDSCs are exposed to slightly rougher and more oxidized GO substrates (rGO 90) . The greater reduction in cell size of cells exposed to rGO 90 compared to rGO 200 is associated with the activation of apoptosis processes. Taken together, the exposure of MDSCs to GO substrates with different redox state and roughness appears as a good strategy to control MDSC activity in vitro . This versatility of GO nanomaterials and the impact of their physico-chemical properties in immunomodulation open the door to its possible selective therapeutic use for pathologies where MDSCs need to be enhanced or inhibited.

GRAPHENE OXIDE AS A NOVEL IMMUNOTHERAPY TOOL FOR THE MODULATION OF MYELOID-DERIVED SUPPRESSOR CELL ACTIVITY IN THE CONTEXT OF MULTIPLE SCLEROSIS