Ocular Immune Privilege Cheat Sheet

Due to not containing lymphoid cells and other common defense mechanisms found throughout the rest of the body, the eye keeps the immune cells it does have at a relative distance which creates a time delay between the introd­uction of a pathogen and the eye mounting an immune response. To combat this, the eye mounts other preven­tative measures in the form of tear secretion that serves to moisten and provide nutrients for the surface of the eye, as well as containing lysozyme, which is antiba­cterial in nature.

There are two types of immune responses the human eye is capable of; innate immune responses and acquired immune responses, both of which serve two distinct purposes from each other. The innate immune response is more broad in its protection as it defends against pathogens and other foreign particles in a non-di­scr­imi­natory manner, such as the eyelid. The main advantage of this is that it typically retains its effect­iveness throughout your lifetime and is present from birth. Other components of the innate immune system include tears. epithelial cells, kerato­cytes, corneal nerves, and interf­erons.

The concept of ocular immune privilege has been around since the 1940's. Since then, further unders­tanding of this concept has allowed for seamless foreign tissue grafting and transp­lants in the eye without the need for constant immuno­sup­pre­ssants. This is due to the body trying to preserve vision my limiting inflam­matory and immune responses to vulnerable or vital areas of the body. This response, or the lack thereof, is promising in that it holds the ability to teach us how to apply this immune privilege to other procedures that typically require someone to be on immuno­sup­pre­ssants for the rest of their lives such as organ transp­lants.

The other form of immune response the eye is capable of is referred to as the acquired immune response. This response is pathog­en-­spe­cific and is cell mediated. These responses are thought to be controlled by Langerhans cells found in the cornea. Langerhans cells are antige­n-p­res­enting cells that take a sample of the pathogen in order to elicit an immune response. However, this has its downsides, being which it can cause damage to surrou­nding tissue that may result in vision loss. This response is more efficient and slow acting than the innate immune response.