Ocular immune system

Its constant exposure to the exterior world means that it is vulnerable to a wide range of microorganisms while its moist mucosal surface makes the cornea particularly susceptible to attack.

The most important function of the cornea is to transmit and refract light so as to allow sharp (high-resolution) images to be produced on the back of the retina.

They provide an inherent barrier against corneal infection while also serving as a primary mode of defense that is present from birth.

MALT is a major component in all mucosal organs, including the respiratory, genital, digestive, and ocular tracts.

[6] Generally, both pathways lead to activation and migration of immune cells within the mucosal tissues, including the conjunctiva.

The conjunctiva covers the sclera, or whites of the eyes, as well as the insides of the eyelids and provides nutrients to underlying and surrounding tissue.

Not only does the conjunctiva produce IgA, like the lacrimal glands, but it also contains macrophages, neutrophilic granulocytes, mast cells, lymphocytes, and other aspects of the general mucosal immune system.

[8] These play a role in creating a smooth surface to facilitate refraction, lubricating the movement of the eyelid, passively transporting gases such as oxygen and carbon dioxide, and protecting the cornea.

Along with another immunoglobulin present in the tear film, IgG, IgA can also neutralize viruses and bind to bacteria, aiding in their detection via other pathways.

Corneal epithelial cells present a physical barrier to prevent microbes from reaching the interior of the eye chamber, which is effectively separated from the rest of the body via tight junctions.

The primary role of this sparse population of cells is thought to be in maintaining the extracellular matrix of collagen lamellae that surround them.

The latter, defensins, have a wide range of antimicrobial affects against bacteria, fungi, and viruses, as well as effects in accelerating healing of damaged epithelial cells.

This leads to reflexive reactions such as increased lacrimal secretion, blinking, and release of neuropeptides, which can induce cytokine activation.