Today, the neurotoxic and neuroprotective roles of the innate immune reactions in ageing, brain injury, autoimmune and neurodegenerative disorders of the CNS are widely investigated and highly debated research topics. Nevertheless, several issues remain to be elucidated, notably the earlier cellular events that initiate dysregulation of brain inflammatory pathways. This book has been prepared to provide an overview of the field of neuroimmunology research.