Nerve growth factor (NGF) is a neurotrophic factor and neuropeptide primarily involved in the regulation of growth, maintenance, proliferation, and survival of certain target neurons. NGF-β acts through its receptor β-NGFR and is involved in the development and maintenance of the sensory and sympathetic nervous systems. NGF-β also is also involved in the growth, differentiation, and survival of B lymphocytes. Human, mouse and rat proteins show cross-reactivity.