Purpose: To study pathologic roles of the presence of serum autoantibodies against retinal ganglion cells in patients with glaucoma.
Methods: Serum autoantibody reactions were detected by Western blot analysis using retinal soluble fractions in 79 patients with glaucoma (normal-tension glaucoma [NTG], 23 cases; primary open-angle glaucoma [POAG], 56 cases) and 60 age-matched healthy subjects. Clinical characteristics including visual acuity, visual field, intraocular pressure (IOP), and optic disc features were compared between the serum autoantibody-positive and -negative patients. The retinal autoantigen recognized by patients' sera was identified by a combination of in-gel digestion and Edman sequencing.
Results: Western blot analysis revealed that serum autoantibody against retinal 50-kDa antigen was recognized in 20 out of 79 glaucoma patients (25.3%; 14 POAG and 6 NTG patients) and 60 age-matched control subjects (11.7%), respectively. Immunocytochemistry revealed that labeling of the ganglion cell layer (GCL) by IgG from glaucoma patients (POAG: 13/56, 23.2%; NTG: 6/23, 26%) existed at a significantly higher rate than that by IgG from control subjects (2/60, 3.3%; P < 0.05). In POAG, maximum IOP in the serum antibody positive-patients was significantly lower than that in the antibody-negative patients (P < 0.05). However, no statistical differences were observed in visual field loss, disc cupping, and other clinical factors between the antibody-positive and -negative groups in POAG and NTG. In-gel digestion of the 50-kDa band in two-dimensional polyacrylamide gels and Edman sequence analysis of the high-performance liquid chromatography-purified peptides identified the 50-kDa protein as gamma-enolase. Injection of the 50-kDa IgG from glaucoma patients or anti-gamma-enolase serum into the vitreous cavity of Lewis rats caused reduction of the b-wave of the electroretinogram and TdT-dUTP terminal nick-end labeling (TUNEL)-positive staining within the GCL.
Conclusions: In the current study, serum autoantibody against 50-kDa protein identified as gamma-enolase in 25% of glaucoma patients.