Increased plasma levels of nerve growth factor in vernal keratoconjunctivitis and relationship to conjunctival mast cells.

PURPOSE: To evaluate the nerve growth factor (NGF) plasma concentration in patients with vernal keratoconjunctivitis and to correlate it with the histopathology and immunopathology of the disease. METHODS: An immunoenzymatic assay was performed to measure NGF plasma levels in patients with vernal keratoconjunctivitis and in healthy matched controls. A competitive radioimmunoassay was used to detect eosinophil cationic protein (ECP) and total specific immunoglobulin E (IgE) serum levels. Histologic evaluation was performed in tarsal and bulbar conjunctival biopsies. RESULTS: Plasma levels of NGF were significantly higher (P < 0.001) in patients with vernal keratoconjunctivitis (mean = 8224.47 +/- 7802.53 pg/ml; median = 121 pg/ml) than in controls (mean = 51.68 +/- 5.94 pg/ml; median 42.5 pg/ml). Conjunctival tissue showed a significant increase of mast cells, eosinophils, and lymphocytes in vernal keratoconjunctivitis. A significant correlation was observed between plasma levels of NGF and the number of mast cells in the tarsal conjunctiva (Cc = 0.81; P < 0.005) and bulbar conjunctiva (Cc = 0.77; P < 0.01) of patients with vernal keratoconjunctivitis. No correlation was found between NGF plasma levels and total IgE serum levels in patients with vernal keratoconjunctivitis; NGF plasma levels were inversely related to the number of circulating eosinophils (Cc = -0.61; P < 0.05) and to the increased serum levels of ECP (Cc = -0.71; P < 0.02). CONCLUSIONS: These data represent the first reported evidence of increased NGF plasma levels in an allergic human disease and suggest a possible relationship between this neurotrophic polypeptide and inflammatory cells in vernal keratoconjunctivitis.