Journal of Eye & Cataract Surgery Open Access

Introduction

The lack of vasculature led scientists to believe immune cells,which travel via the bloodstream, couldn't get to this part of thebody either. But a few years ago, Jefferson researcherschallenged this long held assumption by demonstrating thatimmune cells populate the lens in response to degeneration.Now the Jefferson team finds the eye also launches an immuneresponse in the lens after injury. The discovery adds to a growingbody of evidence that is working to overturn the accepteddogma of the field. "Why would we evolve a tissue that is socentral to our being able to see without ways to ensure itsprotection, its ability to repair itself?" says, Sue Menko, PhD,Professor in the Department of Pathology, Anatomy and CellBiology at Thomas Jefferson University, who led the research."Immune cells are central to that protection and repair." Thelens of the eye works like a camera lens. Its main purpose is tofocus images coming in through the cornea - the transparentfront layer of the eye - onto the retina at the back of the eye."This is really the firstdemonstration that surveillance byimmune cells of the lens in response to injury somewhere else inthe eye," Dr. Menko says. The researchers also found that someimmune cells were able to cross the lens capsule, a membranousstructure that helps to keep the lens under tension.

The results could point to a role for immune cells in cataractformation. Together, the findings indicate that in response todamage or disease, the eye utilizesalternative mechanisms -rather than direct contact with the bloodstream like non-transparent tissues do - to ensure that immune cells get to sitesto provide healing and protection. "We're excited to go fromthinking this doesn't make sense to proving that the body isamazing and can adapt to anything. You just have to go in andlook for it," Dr. Menko says. "We should be willing to challengedogma because that's where discovery is," she adds. "It canenlighten what we know if we always keep our mind open towhat doesn't make sense and what maybe should be challengedto understand things better. The lens of the eye is an unusualorgan. Unlike most of the body's organs, blood vessels don'treach the lens. If they did, they'd obscure our vision and wewouldn't be able to see. The images are detected by the retinaand then translated in the brain as what we see. That lens mustbe crystal clear.

As a result, scientists have always described the lens as atissue without vasculature and therefore no source of immunecells either. The puzzle led Dr. Menko and her team toinvestigate whether immune cells are present in the eye. In aprevious study, they discovered that when the lens is in adiseased state, immune cells are not only recruited there, butthey also show up in the cornea, retina, and vitreous body - allparts of the eye that don't normally have immune cells. Dr.Menko's work suggested that the immune cells come from theciliary body, a sort of muscle that helps squeeze and pull thelens, changing its shape, and helping it focus. Now, in the latestwork, Dr. Menko and colleagues show that after injury to thecornea, immune cells travel from the ciliary body to the lensalong fibers known as ciliaryzonules. The researchers usedfluorescent markers and high-powered microscopes to observestructures of mouse eyes one day after receiving a scratch onthe cornea. The high-tech imaging analysis Dr. Menko's teamused revealed that following injury to the cornea, the immunesystem launches a response to protect the lens. Immune cellsare recruited to the lens via the ciliaryzonules, and crawl alongthe surface of the lens to surveille and protect from adverseimpacts of the corneal wound