Retinal pigment epithelium-immune system interactions: Cytokine productionand cytokine-induced changes

Vision is dependent on proper function of several intraocular structures. I mmune responses to eliminate invading pathogens from the eye may threat vis ion by causing damage to these structures. Therefore, immunological defence of the eye should be carefully balanced between efficacy and maintenance o f Functional integrity. The eye is equipped with several regulatory mechani sms to prevent certain immune and inflammatory responses and is, therefore. regarded as an immune privileged site. The retinal pigment epithelium (RPE ) contributes to the immune privileged status of the eye as part of the blo od-eye barrier and bq the secretion of immunosuppressive factors inside the eye. RPE cells, however, may also play an important role in the developmen t of immune and inflammatory responses in the posterior part of the eye. Du ring the last decade it has become clear that RPE cells are highly sensitiv e to a variety of inflammatory cytokines. Under inflammatory conditions. RP E cells produce a myriad of cytokines that may activate the resident ocular cells or attract and activate leukocytes. Cytokine stimulation of RPE cell s causes profound effects. including nitric oxide secretion, cell surface e xpression of MHC class II and adhesion molecules and abrogation of barrier function. This article provides a comprehensive review of the literature co ncerning RPE cells and cytokines. (C) 2000 Elsevier Science Ltd. All rights reserved.