Scientists at Schepens Eye Research Institute have shown for the first time that a laser burn to one retina can cause both eyes to lose a special protective ability known as immune privilege. Immune privilege protects the eye without the inflammation of the body’s normal immune response, which can further damage delicate eye tissue. This finding, published in the February 2009 American Journal of Pathology, has implications for treating patients with laser burns sustained on the battlefield and in other modern settings.
The discovery is also significant because it suggests a previously unknown communication between the two eyes. “This deepens our understanding of the way immune privilege works,” says Dr. Joan Stein Streilein, principal investigator of the study and senior scientist at Schepens Eye Research Institute.
Immune privilege is a modification of the body’s normal immune response. It protects the eye, the brain and the reproductive system without the full-blown immune response that uses inflammation to violently reject foreign tissue or invaders.
While inflammation in other parts of the body is a useful battle between immune and foreign cells, it is too aggressive for fragile eye, brain and reproductive tissues, and, in the case of the eye, can even lead to blindness. Immune privilege, which intervenes in the battle, is also what prevents the eye from rejecting corneal transplants, making them the most common and successful of transplanted tissues.
In her laboratory, Stein-Streilein and her team made tiny laser burns in one of the retinas of 15 mice. They then injected either the burned or the unburned eyes of each mouse with the antigen, Ovalbumin. Antigens are substances that the body perceives as foreign and against which it mounts a defense.
They found that immune privilege was disrupted in both eyes after six hours and continued to be disrupted even after 56 days.
When they injected the same antigen into the eyes of a group of control mice without burns, they observed no inflammation.
Since created in the 1960s, lasers have found their way onto the battlefield, into the operating rooms and into modern research laboratories. While ophthalmologists have been aware of the local damage done by laser burns to retinas, they have not been tuned into the possibility of long-term loss of immune privilege in one or both eyes.
Understanding mechanisms that destroy or disrupt immune privilege will ultimately lead to novel therapies to restore that special privilege not only in the eye but in the brain and the reproductive system as well, she adds.
The next steps for the team will be to study the novel mechanisms that allow for communication between the injured and non-injured eye.
Other scientists involved in the study include: First author, Hong Qiao, MD, PhD, and second author Kenyatta Lucas, PhD, both scientists at Schepens.
Schepens Eye Research Institute is an affiliate of Harvard Medical School and the largest independent eye research institute in the nation.
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