When can your immune system attack your own eyes?

Interestingly, certain areas of the body have something called immune privilege. This means that the body’s normal inflammatory immune response is limited here. Scientists think the purpose of immune privilege is to protect these important areas from damage that may occur with swelling and higher temperatures from the immune response. The eye is one of a few areas of the body with immune privilege. The eye limits its inflammatory immune response so that vision isn’t harmed by swelling and other tissue changes. Other sites with immune privilege include the brain, testes, placenta and fetus.

The eyes have their own special immune system. It keeps their delicate parts safe. This system is key to keeping our vision clear and protecting our eyes from harm.

This immune defense is not just a simple shield. It’s an active process that involves many cell types and steps. Localized immune cells are very important in this fight.

Localized Immune Cells in the Eye

The eye has different types of immune cells that help defend it. These include:

• Macrophages, which clean up and destroy harmful cells and germs
• Dendritic cells, which help T-cells fight off infections
• T-cells themselves, which are key in cell-based immunity

These cells work together to keep the eye safe from invaders. 

But an eye injury can trigger the immune system to attack the eye, even the other eye, because trauma can break down the eye's natural "immune privilege," revealing normally hidden proteins that the body's immune cells then recognize as foreign, leading to inflammation and potential damage in a condition called sympathetic ophthalmia, or similar autoimmune responses.
How does this happen? 
Immune Privilege: The eye is normally shielded from the immune system to prevent inflammation from affecting vision.
Trauma Breaks the Shield: An injury (like a penetrating wound or severe inflammation) disrupts this barrier, allowing immune cells to see the eye's internal proteins.
Molecular Mimicry: The immune system, fighting the injury, may mistake these eye proteins for invaders, potentially due to similarities with antigens from infections (molecular mimicry).
Attack on Both Eyes: This mistaken attack can then spread to the uninjured eye, causing inflammation (uveitis) and vision loss, a condition related to sympathetic ophthalmia.
Examples of Immune Attacks on Eyes
Sympathetic Ophthalmia: Inflammation in one eye after injury triggers an autoimmune response in the other.
Autoimmune Uveitis: The immune system attacks the eye's middle layer, causing pain, redness, and blurry vision.
Thyroid Eye Disease (TED): Immune system targets tissues around the eyes, causing bulging and double vision.

Risk Factors for Developing Autoimmune Eye Conditions

While anyone can get an autoimmune eye condition, some factors raise the risk. These include:

• Family history: If your family has autoimmune diseases, you’re more likely to get one too.
• Existing autoimmune conditions: People with other autoimmune diseases are at higher risk for eye conditions.
• Environmental exposures: Things like UV radiation or certain chemicals might increase your risk.

Knowing these risk factors and what causes autoimmune responses helps us understand autoimmune eye diseases better. It shows why we need specific treatments for these conditions.

So how can you protect your eyes?
Seek immediate medical attention for any eye injury.
Early diagnosis and management are crucial to prevent long-term vision loss.