Tolerogenic Dendritic Cells as a Promising Antigen-Specific Therapy in the Treatment of Multiple Sclerosis and Neuromyelitis Optica From Preclinical to Clinical Trials

The identification of activated T lymphocytes restricted to myelin-derived immunogenic peptides in multiple sclerosis (MS) and aquaporin-4 (AQP4) water channel in neuromyelitis optica (NMO) in the blood of patients opened the possibility for developing highly selective and disease specific therapeutic approaches. Antigen presenting cells (APCs) and in particular dendritic cells (DCs) represent a strategy to inhibit pro-inflammatory T helper cells. DCs are located in peripheral and lymphoid tissues and are essential for homeostasis of T cell-dependent immune responses. The expression of a particular set of receptors involved in pathogen recognition confers to DCs the property to initiate immune responses. However, in the absence of danger signals different DC subsets have been revealed to induce active tolerance by inducing regulatory T cells, inhibiting pro-inflammatory T helper cells responses or both. Interestingly, several protocols to generate clinical grade tolerogenic DC (tol-DCs) in vitro have been described, offering the possibility to restore the homeostasis to CNS related antigens. In this review, we discuss about different DC subsets and their role in tolerance induction, the different protocols to generate tol-DCs and preclinical studies in animal models as well as describe recent characterization of tol-DCs for clinical application in autoimmune diseases and in particular in MS and NMO patients. In addition, we discuss the clinical trials ongoing based on tol-DCs to treat different autoimmune diseases.