Nerve growth factor and neuroimmune interactions in inflammatory diseases.

Discovered almost 50 years ago, nerve growth factor (NGF) has been extensively studied in various biological systems. NGF has recently been suggested to play an important role in mediating and/or regulating immune response, in addition to its trophic and tropic effects on nerve growth and regeneration It is clear that in complex interactions between immune cells and nervous system NGF plays a central role. We have only just begun to identify and understand the direct mechanisms by which NGF activates target cells, the precise identity of the target cells, and the particular factors released from target cells. Nerve growth factor together with possibly other neurotrophins such as BDNF (brain-derived nerve growth factor), GDNF (glial-derived nerve growth factor) or NT3 are important modulators of immunity. More detailed studies are needed at the receptor, mediator and cellular levels to better understand the neuroimmunomodulatory properties of neurothrophins and NGF. The nature of the involvement of NGF in inflammation and inflammatory diseases remains a particularly interesting question. By blocking NGF or mediators released upon NGF activation, we are able to control the progress of inflammation, thereby opening many therapeutic opportunities for the future.