Institute of Animal Physiology, Department of Veterinary Sciences, Faculty of Veterinary Medicine, LMU Munich, München, Germany.
Invest Ophthalmol Vis Sci. 2012 Jan 25;53(1):294-300. doi: 10.1167/iovs.11-8734.
Although the presence of IgG autoantibodies in the vitreous of spontaneous cases of equine recurrent uveitis (ERU) has been demonstrated, the potential role of IgM reactivities during ERU pathogenesis remains unexplored. The purpose of this study was to examine the presence of IgM autoantibodies in vitreous specimens of ERU-affected horses and to test their binding specificity to intraocularly expressed proteins.
To test IgM autoantibody responses to retinal tissue, vitreous samples of eye-healthy controls and ERU patients were analyzed via two-dimensional Western blot analysis with equine retinal tissue as an antigen source. A candidate protein, the peptide neurofilament medium (NF-M), was identified via mass spectrometry and validated via enzyme-linked immunosorbent assay. Immunohistochemistry for NF-M expression was performed on healthy and ERU-affected retinal sections.
Whereas autoreactivity was never detected in the healthy vitreous samples, NF-M was specifically targeted by vitreal IgM autoantibodies in 44% of the ERU cases. Vitreal anti-NF-M IgG was detected in only 8% of the ERU samples, pointing to a persistent IgM response. In healthy horse retina, NF-M was located in the retinal ganglion cells and their processes, with additional staining in the outer plexiform layer. NF-M expression in ERU-affected retinas decreased considerably, and the remaining expression was limited to the nerve fiber layer.
Intraocular anti NF-M IgM autoantibodies occur with high prevalence in vitreous of spontaneous autoimmune uveitis cases. The IgM dominated response may indicate a thymus-independent response to NF-M and merits further investigation in ERU, as well as in its human counterpart, autoimmune uveitis.
尽管已经证明，在自发性马复发性眼葡萄膜炎（ERU）的玻璃体内存在 IgG 自身抗体，但在 ERU 发病机制中 IgM 反应的潜在作用仍未得到探索。本研究的目的是检查 ERU 受影响马的玻璃体内是否存在 IgM 自身抗体，并测试其对眼内表达蛋白的结合特异性。
为了测试针对视网膜组织的 IgM 自身抗体反应，通过二维 Western blot 分析用马视网膜组织作为抗原来源，分析了健康对照组和 ERU 患者的玻璃体样本。通过质谱鉴定出一种候选蛋白，即肽神经丝中间（NF-M），并通过酶联免疫吸附试验进行验证。对健康和 ERU 受影响的视网膜切片进行 NF-M 表达的免疫组织化学染色。
在健康的玻璃体样本中从未检测到自身反应，而在 44%的 ERU 病例中，NF-M 特异性地被玻璃体内 IgM 自身抗体靶向。仅在 8%的 ERU 样本中检测到玻璃体抗-NF-M IgG，表明存在持续的 IgM 反应。在健康马的视网膜中，NF-M 位于视网膜神经节细胞及其突起中，在外丛状层中还有额外的染色。在 ERU 受影响的视网膜中，NF-M 的表达明显减少，并且剩余的表达仅限于神经纤维层。
在自发性自身免疫性葡萄膜炎病例的玻璃体中，眼内抗 NF-M IgM 自身抗体的发生率很高。以 IgM 为主的反应可能表明对 NF-M 的非胸腺依赖性反应，值得在 ERU 以及其人类对应物，自身免疫性葡萄膜炎中进一步研究。
