Interactions of the nervous and immune systems in development, normal brain homeostasis, and disease

Neurotransmitters, neuropeptides, neurotrophins, and neuroendocrine hormones have traditionally been assigned functions in normal development and homeostasis of neuronal networks; cytokines and adhesion molecules have been assigned functions within the peripheral immune system. Molecular dissection of the presence and function of these receptors and ligands during development of the immune and nervous systems, in normal healthy adult central and peripheral nervous tissue, and in the pathological response of immune elements in the brain and neuroelements in the immune system has forced us to alter these long-held concepts. Examples of how glia and neurons function in relationship to these paracrine and autocrine stimuli in health and disease are provided in this short review.