Ciliary Neurotrophic Factor (CNTF) is a potent survival factor for neurons and oligodendrocytes. CNTF has also been shown to prevent the degeneration of motor axons after axotomy. CNTF is highly conserved across species and exhibits cross-species activities. Human and rat CNTF share approximately 83% homology in their protein sequence. CNTF is structurally related to IL6, IL11, LIF and OSM. All of these four helix bundle cytokines share gp130 as a signal transducing subunit in their receptor complexes. CNTF, like FGF acidic, FGF basic, and PD-ECGF (platelet-derived endothelial cell growth factor), does not possess a signal sequence that would allow secretion of the factor by classical secretion pathways. The mechanism underlying the release of CNTF is unknown.