Substantial evidence indicates a dysfunctional communication between the sympathetic nervous system and the immune system in Th1-mediated autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis. In this Opinion, we propose that the sympathetic regulation of immunity is not only mediated by catecholamines but also involves neuropeptide Y (NPY), an additional postganglionic SNS transmitter that is shown to modulate various immunological functions in vitro and in vivo. Based on recent experimental findings, we believe that a more precise understanding of the role of NPY in the regulation of autoimmune Th1 cells will provide novel insights into the neuroimmunological basis of autoimmunity.