NGF is purified in three forms: the 7S, 2.5S and β. The 7S, 130 kDa, form occurs naturally in mouse submaxillary glands, and is a multimeric protein composed of two α, one β and two γ subunits. The name is derived from its sedimentation co-efficient, 7S. The biologically active subunit is the β, which is a 26 kDa dimer composed of two identical 120 amino acid chains held together by hydrophobic interactions.5 The 2.5S form is 9 amino acids shorter than the β form, because of proteolysis that occurs during the purification process.6 The structural hallmark of all the neurotrophins is the characteristic arrangement of the disulfide bridges known as the cysteine knot, which has been found in other growth factors such as PDGF.7 There is a 95.8% homology between the rat and mouse forms, and a 85% homology between the human and mouse. nNGF has been shown to regulate neuronal survival, development function and plasticity.8 Recently, involvement of NGF in processes not involving neuronal cells has been shown, such as asthma,9 psoriasis10 and wound healing.The biological effects of NGF are mediated by two receptors: TrkA, which is specific for NGF, and p75, which binds all the neurotrophins.