Microglia Are the Key Players in Photoreceptor Damage Response in the Retina, Not Neutrophils

Recent research conducted by scientists at the Flaum Eye Institute and Del Monte Institute for Neuroscience at the University of Rochester has uncovered new insights into how the retina responds to damage. Traditionally, immune responses to tissue injury in the body involve neutrophils, which are rapidly recruited blood cells that act as the first line of defense. However, this study reveals that the retina exhibits a unique immune response. When photoreceptor cells—the light-sensitive cells crucial for vision—are damaged, microglia, the resident immune cells in the brain and retina, are the primary responders.

Using advanced imaging techniques, including adaptive optics imaging developed at the University of Rochester, researchers visualized individual cells within the living eye of mice with damaged photoreceptors. The striking discovery was that, despite neutrophils passing through nearby blood vessels, they were not recruited to the injury site. Instead, microglia activated and responded directly to the damage. This suggests a form of immune cell 'cloaking' during retinal injury, likely a protective mechanism to prevent excessive inflammation that could worsen damage.

"What’s remarkable here is that the neutrophils, which are usually the first responder in other tissues, do not signal to microglia during retinal injury," explained Jesse Schallek, Ph.D., senior author of the study. "This indicates that the retina employs a different immune strategy, possibly to shield itself from harmful immune responses."

Photoreceptors are unique to the retina and are essential for converting light into signals sent to the brain, enabling vision. Diseases such as age-related macular degeneration, retinitis pigmentosa, and cone-rod dystrophy involve the loss of these cells, yet there are currently no cures. Understanding the cellular interactions during damage and repair opens the door for developing targeted therapies.

The study’s first author, Derek Power, and collaborators hope that these findings will influence future treatments aimed at preserving or restoring photoreceptors by manipulating microglia or immune responses without triggering potentially damaging inflammation. This research underscores the importance of the eye’s specialized immune environment, which differs significantly from other tissues.

Source: ScienceX - https://medicalxpress.com/news/2025-07-microglia-neutrophils-photoreceptor-retina.html