Role of Fas Ligand in Ocular Tissue

The expression of Fas ligand (FasL) in the eye is an important factor in the maintenance of immune privilege. Although FasL expression in donor corneas contributes to prolonged survival of orthotopic corneal allografts in solid organ transplantation, FasL gene-transfected tissues reportedly lead to graft destruction through neutrophil recruitment. Differences in the effects of FasL have been attributed to different roles of soluble FasL (sFasL) and membrane FasL (mFasL). This is based on the presumption that the signals through sFasL and mFasL differ, with one causing apoptosis and the other activating inflammation. It was recently reported that inflammation caused by FasL was inhibited at an immune-privileged site, and therefore the effects of FasL may depend on differences in the anatomic sites where FasL-expressing cells are located. In this article, we discuss the role of sFasL and mFasL in ocular immune privilege.