Zamiri Parisa, Masli Sharmila, Kitaichi Nobuyoshi, Taylor Andrew W, Streilein J Wayne
Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
Invest Ophthalmol Vis Sci. 2005 Mar;46(3):908-19. doi: 10.1167/iovs.04-0362.
The role of thrombospondin (TSP)-1 in TGF-beta activation and T-cell suppression was studied in the retinal pigment epithelial (RPE) cells, a monolayer of pigmented cells that line the subretinal space, an immune-privileged site in the eye.
Posterior eyecups were prepared by excising the anterior segment, lens, and retina from enucleated eyes of C57BL/6, thrombospondin-1 knockout (TSP-1KO), and TGF-beta2 receptor II double-negative (TGF-beta2 RII DN) mice, leaving behind a healthy monolayer of RPE resting on choroid and sclera. Serum-free medium was added to these RPE eyecups, and, after various time intervals, supernatants (SNs) were removed and tested.
SNs of an ex vivo culture of RPE cells from C57BL/6 mice were shown to inhibit both antigen and anti-CD3 activation of T cells, partially due to constitutive production of TGF-beta and to the ability of RPE to activate the latent form of TGF-beta. Activation of TGF-beta was entirely dependent on TSP-1, also produced by RPE. SNs of RPE from TSP-1KO mice failed to inhibit T-cell activation. Ovalbumin (OVA)-specific delayed hypersensitivity (DH) was not impaired when OVA was injected either into the subretinal space or into the anterior chamber of TSP-1KO mice before OVA immunization. Moreover, experimental autoimmune uveoretinitis was significantly more intense in eyes of TSP-1KO mice and failed to undergo spontaneous resolution unlike wild-type mice.
Production of both TSP-1 and active TGF-beta by RPE is essential to the creation and maintenance of immune privilege in the subretinal space and that the immune privilege limits the severity and duration of retinal inflammation due to autoimmunity.
研究血小板反应蛋白（TSP）-1在视网膜色素上皮（RPE）细胞中转化生长因子（TGF）-β激活及T细胞抑制中的作用，RPE细胞是位于视网膜下间隙（眼部的一个免疫赦免部位）的单层色素细胞。
通过切除C57BL/6小鼠、血小板反应蛋白-1基因敲除（TSP-1KO）小鼠及TGF-β2受体II双阴性（TGF-β2 RII DN）小鼠摘除眼球的前段、晶状体和视网膜来制备后眼杯，留下一层健康的RPE细胞单层置于脉络膜和巩膜上。向这些RPE眼杯中加入无血清培养基，在不同时间间隔后，取出上清液（SNs）并进行检测。
来自C57BL/6小鼠的RPE细胞体外培养上清液显示可抑制T细胞的抗原及抗CD3激活，部分原因是TGF-β的组成性产生以及RPE激活潜伏形式TGF-β的能力。TGF-β的激活完全依赖于RPE也产生的TSP-1。TSP-1KO小鼠的RPE上清液未能抑制T细胞激活。在卵清蛋白（OVA）免疫前将OVA注入TSP-1KO小鼠的视网膜下间隙或前房时，OVA特异性迟发型超敏反应（DH）并未受损。此外，TSP-1KO小鼠眼中的实验性自身免疫性葡萄膜视网膜炎明显更严重，且与野生型小鼠不同，未能自发消退。
RPE产生TSP-1和活性TGF-β对于在视网膜下间隙建立和维持免疫赦免至关重要，且该免疫赦免限制了自身免疫引起的视网膜炎症的严重程度和持续时间。
