How Does the Eye's Immune-Privileged Site Defend Itself?

Discover how the eye's immune-privileged site defends itself. Explore tear composition and the ocular surface.

How Does the Eye's Immune-Privileged Site Defend Itself?
Photo by Milada Vigerova / Unsplash

Contrary to popular belief, the eye lacks a traditional immune system found in other parts of the body.

While the cornea and the aqueous humour have certain defense mechanisms, they don't function in the same way as the immune system found in the rest of the body.

The eye is considered an immune-privileged site, which means it has unique immune responses.

External Protection

The ocular surface, including the conjunctiva and the tissue around the eye, are generally protected by the body's immune defenses.

Any infection or injury occurring to these parts is usually resolved through the immune response generated in this surrounding tissue, not within the eyeball itself.

The Role of Tears

Tears are an essential part of protecting the eye.

They contain lysozyme, an enzyme that damages the cell walls of certain bacteria.

Additionally, tears help flush away any foreign substances or irritants present on the ocular surface, preventing infections from taking hold.


The eye has its own microbiota, a collection of microorganisms living on its surface.

This microbiota, comprising bacteria, viruses, and fungi, plays a crucial role in maintaining ocular health.

Recent research has indicated that these microorganisms may also assist in preventing infections by outcompeting potentially harmful pathogens.

Self-Healing Ability

The body has a remarkable ability to fight off infections without the need for medical intervention.

When the eye's external defense mechanisms are functioning optimally, they can often eliminate minor infections without the need for medical treatment.

Environmental Factors and the Immune Response

Environmental factors such as humidity, ultraviolet light, and airflow play a role in the eye's ability to resist infections.

The eye's exposure to these elements can influence the immune response and its ability to naturally resolve infections.

The human body's ability to naturally combat infections, even within immune-privileged sites like the eye, is a testament to its complex and efficient defense mechanisms.