Eye Will Remember That

Do eyes remember the battles they have fought? The results of a study by researchers from the Peter Doherty Institute for Infection and Immunity in Melbourne, Australia, suggest that they do. For the first time, tissue-resident memory T cells have been imaged patrolling the corneas of healthy subjects, providing local protective immunity (1). This challenges the current understanding that these long-lasting immune cells do not remain in the corneas of healthy individuals due to the eye’s immune-privileged nature, which tempers immune responses to protect vision.

As lead author Scott Mueller, Professor, NHMRC Senior Research Fellow and laboratory head in the Department of Microbiology and Immunology, explains, “We knew that T cells can be found in most body surfaces, such as the skin, where they lie in wait and can protect us from infections. Although the cornea has ways to protect itself from infections, including via T cells, we did not know whether T cells can stay in the cornea as a ‘memory’ of infection.” To examine the question, Mueller and his team used multiphoton microscopy to study the corneas of mice infected with ocular herpes simplex virus (HSV). They observed the production of T cells within the murine corneas in response to the virus and observed that memory T cells remained after the infection was fought off to protect against future reinfection. These results came alongside the aforementioned in vivo confocal microscopy images of memory T cells within healthy human corneas, strengthening the likelihood of immune memory within the human eye.

Although the results of this study are promising and may even lead to therapeutic avenues for ocular infectious diseases, the researchers acknowledge that their results must first be confirmed in a wider population. Additionally, a greater understanding of T cells’ role in the cornea is needed to rule out the possibility that their presence may reflect or even precipitate disease. Mueller explains, “We are planning to study immune cells from the cornea in people and determine how these contribute to the health of the eye, with the goal of identifying ways in which we can improve immunity to infections such as HSV and potentially control unwanted immune responses, such as those that occur during dry eye disease.”