In retinal neurodegeneration associated with glaucoma and diabetic retinopathy, proNGF stimulates p75NTR-dependent production and secretion of TNFα and α2-macroglobulin (α2M) by activated glia.19, 20, 21, 22, 23 These are neurotoxic factors that trigger neuronal death in a paracrine manner. The gene discussed is TNF; the disease is diabetic retinopathy.