Human β-Nerve Growth Factor (β-NGF) was initially isolated in the mouse submandibular gland. It is composed of three non-covalently linked subunits α, β, and γ; it exhibits all the biological activities ascribed to NGF. It is structurally related to BDNF, NT-3 and NT-4 and belongs to the cysteine-knot family of growth factors that assume stable dimeric structures. Β-NGF is a neurotrophic factor that signals through its receptor β-NGF, and plays a crucial role in the development and preservation of the sensory and sympathetic nervous systems. Β-NGF also acts as a growth and differentiation factor for B lymphocytes and enhances B-cell survival. These results suggest that β-NGF is a pleiotropic cytokine, which in addition to its neurotropic activities may have an important role in the regulation of the immune system. Human β-NGF shares 90% sequence similarity with mouse protein and shows cross-species reactivity.