INCREASED PLASMA-LEVELS OF SUBSTANCE-P IN VERNAL KERATOCONJUNCTIVITIS

Purpose. The increase of nerve growth factor (NGF) plasma levels in ve rnal keratoconjunctivitis (VKC) patients has been demonstrated previou sly. Results of numerous studies in vitro and in vivo have shown that NGF modulates the synthesis of substance P (SP), a neuropeptide involv ed in the pathogenesis of human allergic diseases. In this study the i nvolvement of SP in this allergic conjunctivitis is investigated, alon g with its relationship Kith NGF and other systemic and local markers of VKC. Methods. Competitive radioimmunoassays were used to detect the levels of SP in plasma, the levels of eosinophil cationic protein, an d the total and specific immunoglobulin E in the serum of 11 patients with VKC and in 11 healthy matched controls. Plasma levels of nerve gr owth factor (NGF) were measured in all VKC patients and controls using an immunoenzymatic assay. Histologic evaluation was performed in tars al and bulbar conjunctival specimens obtained in biopsies from 8 VKC p atients and 4 control subjects. Results. Patients with VKC show a sign ificant increase of SP and NGF plasma levels (P < 0.003 and P < 0.001, respectively), and an increase of eosinophil cationic protein and imm unoglobulin E levels in the serum (P < 0.001 and P < 0.002, respective ly). Mast cells, eosinophils, and lymphocytes were also significantly increased in the conjunctiva of VKC patients. Interestingly enough, VK C patients with the highest NGF plasma levels also showed the highest SP levels.Conclusions. The data show the involvement of SP in VKC and suggest that SP with NGF could modulate the allergic response in this disease, probably through an interaction with inflammatory cytokines.