The classical field of neuroimmunology deals with the immune response in infectious, autoimmune-mediated, ischemic, degenerative, traumatic, and neoplastic diseases of the nervous system with a major focus on immune-mediated demyelination. Recently more and more evidence points to a broader interaction between the immune and nervous systems via morphological connections, shared signal molecules and common mechanisms of signal transduction. Consequently, immune processes affect nervous functions and vice versa under both physiologic and pathologic conditions. This includes neuroendocrine (hormonal) and vegetative (neurotransmitter-mediated) influences on the immune response including conditioned immunostimulation and immunosuppression (neuroimmunomodulation) as well as effects of immune mediators (cytokines) on neuronal and psychic functions (psychoneuroimmunology). These findings have a strong impact on future strategies for the treatment of somatic as well as psychiatric diseases.