An investigation of antibodies to nerve growth factor in diabetic autonomic neuropathy

Nerve growth factor (NGF) is required for development and maintenance of autonomic nervous function and is highly expressed in the iris. An association between sensory and autonomic diabetic neuropathy and NGF function has been postulated. In light of the evidence for an autoimmune component to the pathogenesis of autonomic neuropathy in Type 1 diabetes mellitus, an enzyme linked immunosorbent assay (ELISA) was established to investigate the presence of autoantibodies to mNGF in: 20 patients with long-standing Type 1 diabetes with abnormal autonomic function tests, of whom 14 had symptomatic autonomic neuropathy, 3 had an episode of iritis, and 6 had no autonomic symptoms; 9 age-matched patients with Type 1 diabetes and no complications; 10 healthy control subjects. Insulin antibodies by ELISA and autoantibodies to other endocrine targets were also measured. The specificity of anti-mNGF autoantibody ELISA was further confirmed by immunodepletion on mNGF-Sepharose 4B. No differences in antibody binding to mNGF were detected, between any of the patient groups and control subjects. There was no relationship between age, sex, and diabetes duration and mNGF binding. High levels of anti-mNGF autoantibodies were found in only one diabetic patient who had no evidence of neuropathy, raising the possibility that an autoimmune component to NGF might precede the development of autonomic dysfunction. It remains to be established whether autoantibodies to NGF play a role in diabetic autonomic neuropathy and prospective studies will be required to investigate whether the autoantibodies are a feature of evolving but not established neuropathy.