Soluble Fas Ligand and Ocular Immune Privilege

描述（由申请人提供）：Fas配体（FasL）是一种膜结合的可溶性蛋白，两种形式都在免疫特权眼内表达。在我们之前的研究中，我们使用眼部肿瘤模型来证明不同形式的FasL调节眼睛的先天免疫：(i)膜FasL （mFasL）诱导炎症并终止免疫特权，而（ii）可溶性FasL （sFasL）防止炎症并维持免疫特权。因此，鉴于FasL在眼内组成性表达，并且FasL的膜形式是促炎的，我们提出在正常眼睛中：(i) mFasL的促炎功能被阻断，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 blot分析。在正常眼睛中检测到高可溶性FasL （27 kDa）与膜性FasL （38 kDa）之比（10:1）。在FasL基因敲除小鼠的眼睛中，检测到另外3条完全缺失的修饰sFasL条带（28-31 kDa）。改良的sFasL是眼睛所特有的，在其他免疫特权部位（如睾丸）中没有发现。

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.