Brain-Derived Neurotrophic Factor in Neuroimmunology: Lessons Learned from Multiple Sclerosis Patients and Experimental Autoimmune Encephalomyelitis Models

The concept of neuroprotective autoimmunity implies that immune cells, especially autoantigen-specific T cells, infiltrate the central nervous system (CNS) after injury and contribute to neuroregeneration and repair by secreting soluble factors. Amongst others, neurotrophic factors and neurotrophins such as brain-derived neurotropic factor (BDNF) are considered to play an important role in this process. New data raise the possibility that this concept could also be extended to neuroinflammatory diseases such as multiple sclerosis (MS) where autoantigen-specific T cells infiltrate the CNS, causing axonal/neuronal damage on the one hand, but also providing neuroprotective support on the other hand. In this review, we summarize the current knowledge on BDNF levels analyzed in MS patients in different compartments and its correlation with clinical parameters. Furthermore, new approaches in experimental animal models are discussed that attempt to decipher the functional relevance of BDNF in autoimmune demyelination.