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Nerve growth factor (NGF): an important molecule for trophism and healing of the ocular surface.

Nerve growth factor (NGF) is the best-characterized neurotrophin, required for the development and survival of selected neurons including sympathetic and sensory neurons.1 NGF furnishes trophic support after neuronal injuries and reverses pathological changes induced by peripheral nerve injury.2 The biological action of NGF is not restricted to cells of neuronal origin but extends to cells of the immune system.3 In vitro and in vivo studies have shown NGF induces mast cell differentiation, degranulation and mediator release, suppresses leukotriene C4 formation from eosinophils and stimulates T and B lymphocyte proliferation and activation.4 We recently demonstrated a basal production of NGF by T-helper (Th-0, Th-1 and Th-2) cell clones in vitro and an increased production of NGF by Th-2 lymphocytes after activation.5 These findings support the clinical evidence of high circulating NGF levels in autoimmune and allergic diseases in humans.6‘7 In the last 5 years we focused our research on NGF’s role in the modulation of healing and inflammation on the ocular surface. This paper reviews experimental and clinical data of NGF in health and disease of the external eye.