Soluble Fas Ligand and Ocular Immune Privilege

描述（由申请方提供）：Fas配体（FasL）作为膜结合和可溶性蛋白产生，两种形式均在免疫豁免眼内表达。在我们先前的研究中，我们使用眼部肿瘤模型来证明不同形式的FasL调节眼睛中的先天免疫：（i）膜FasL（mFasL）诱导炎症并终止免疫赦免，而（ii）可溶性FasL（sFasL）预防炎症并维持免疫赦免。因此，考虑到FasL在眼内组成性表达，并且FasL的膜形式是促炎性的，我们提出在正常眼中：（i）mFasL的促炎性功能被阻断，和/或（ii）FasL主要以可溶性（抗炎）形式表达。我们的实验数据支持后者。对正常、FasL敲除和慢性炎症的眼睛进行FasL的Western印迹分析。在正常眼中检测到高比例的可溶性（27 kDa）与膜（38 kDa）FasL（10：1）。检测到修饰的sFasL的三个额外条带（28-31 kDa），其在FasL敲除小鼠的眼中完全不存在。修饰的sFasL是眼睛所特有的，在其他免疫特权部位（如睾丸）中未发现。 最后，27 kD和31 kD sFasL条带在缺乏免疫赦免的眼睛中完全缺失，并显示继发于色素分散综合征的慢性炎症。 我们假设修饰的sFasL在眼内表达，并在眼内分泌中起核心作用。 维持免疫特权该假设将在三个特定目的中进行测试：（i）确定sFasL在眼睛中的表达位置以及如何修饰，（ii）确定修饰的sFasL如何刺激先天免疫，以及（iii）确定修饰的sFasL是否控制免疫豁免。我们相信这项研究不仅将促进我们对免疫豁免的理解，而且有助于解释FasL在移植和肿瘤中的生理作用的争议。

DESCRIPTION (provided by applicant): Fas ligand (FasL) is produced as a membrane-bound and soluble protein and both forms are expressed within the immune privileged eye. In our previous studies we used an ocular tumor model to demonstrate that the different forms of FasL regulate innate immunity in the eye: (i) membrane FasL (mFasL) induces inflammation and terminates immune privilege, while (ii) soluble FasL (sFasL) prevents inflammation and maintains immune privilege. Therefore, given that FasL is constitutively expressed within the eye, and the membrane form of FasL is pro-inflammatory, we propose that in a normal eye either: (i) the pro-inflammatory function of mFasL is blocked, and/or (ii) FasL is expressed primarily in the soluble (anti-inflammatory) form. Our experimental data support the latter. Western blot analysis of FasL was performed on normal, FasL knockout, and chronically inflamed eyes. A high ratio of soluble (27 kDa) to membrane (38 kDa) FasL (10:1) was detected in normal eyes. Three additional bands (28-31 kDa) of modified sFasL were detected that were completely absent in the eyes of FasL knockout mice. The modified sFasL was unique to the eye and not found in other immune privileged sites, such as the testis. Finally, the 27kD and 31kD sFasL bands were completely absent from eyes that lacked immune privilege and displayed chronic inflammation secondary to pigment dispersion syndrome. We hypothesize that modified sFasL is expressed within the eye and plays a central role in maintaining immune privilege. This hypothesis will be tested in three Specific Aims (i) determine where sFasL is expressed in the eye and how it is modified, (ii) determine how modified sFasL stimulates innate immunity, and (iii) determine if modified sFasL controls immune privilege. We believe this study will advance not only our understanding of immune privilege, but help explain the controversy over the physiological role of FasL in transplants and tumors.