Defensins: Key Molecules in Ocular Surface Protection

The cornea, the clear tissue at the front of the eye, is responsible for the majority of the optical power of the eye and thus for focusing light on to the retina. However, sitting at the front of the eye as a thinly epithelialized tissue, it is vulnerable to environmental trauma and pathogen invasion. Due to this vulnerability, the mechanisms of innate immunity are critical for routine protection of the cornea as well as the entire visual organ. Inflammation is a common component of many ocular surface diseases as well as the response to infection. Understanding the role of innate immunity in inflammation and particularly the path to the involvement of the systemic immunity is critical in order to minimize the effects of acute and chronic inflammation. In addition to forming a physical barrier, epithelial cells possess multiple molecular mechanisms in pathogen sensing and control of inflammation. In this article, we will review the recent progress in understanding the roles of defensins in combating ocular infection and in the modulation of inflammation. We will also examine the biological activities and regulated expression of defensins in corneal and conjunctival epithelial cells.