Targeting aryl hydrocarbon receptor functionally restores tolerogenic dendritic cells derived from patients with multiple sclerosis.

Multiple Sclerosis (MS) is a chronic disease characterized by dysregulated self-reactive immune responses that damage the neurons' myelin sheath, leading to progressive disability. The primary therapeutic option, immunosuppressants, inhibits pathogenic anti-myelin responses but depresses the immune system. Antigen-specific monocyte-derived autologous tolerogenic dendritic cells (tolDCs) offer alternative therapeutic approaches to restore tolerance to auto-antigens without causing generalized immunosuppression. However, immune dysregulation in MS could impact the properties of the monocytes used as starting material for this cell therapy. Here, we characterized CD14+ monocytes, mature dendritic cells (mDCs) and Vitamin-D3-tolDCs (VitD3-tolDCs) from active, treatment-naive MS patients and healthy donors (HD). Using multi-omics, we identified a switch in these cell types towards proinflammatory features characterized by alterations in the AhR and NF-kB pathways. MS patient-derived VitD3-tolDCs showed reduced tolerogenic properties compared to those from HD, which were fully restored through direct AhR agonism and using in vivo or in vitro Dimethyl Fumarate (DMF) supplementation. Additionally, in the experimental autoimmune encephalomyelitis (EAE) mouse model, combined therapy of DMF and VitD3-tolDCs was more efficient than monotherapies in reducing the clinical score of mice. We propose that a combined therapy with DMF and VitD3-tolDCs offers enhanced therapeutic potential in treating MS.