The focus of this commentary is to describe how neuroscience, immunology, and pharmacology intersect and how interdisciplinary research involving these areas has expanded knowledge in the area of neuroscience, in particular. Examples are presented to illustrate that the brain can react to the peripheral immune system and possesses immune function and that resident immune molecules play a role in normal brain physiology. In addition, evidence is presented that the brain immune system plays an important role in mediating neurodegenerative diseases, the aging process, and neurodevelopment and synaptic plasticity. The identification of these mechanisms has been facilitated by pharmacological studies and has opened new possibilities for pharmacotherapeutic approaches to the treatment of brain disorders. The emerging field of neuroimmune pharmacology exemplifies this interdisciplinary approach and has facilitated the study of basic cellular and molecular events and disease states and opens avenues for novel therapies.