Amazing stuff!
"... The cornea has a dampened response to infection, in part because aggressive immune cells could damage the clear layer of tissue and obstruct vision, ... For this reason, the immune cells that mount a quick but crude response to an infection, such as dendritic cells and macrophages, largely reside in the outer sections of the cornea and emerge only when needed. ...
Using a powerful multiphoton microscope for studying living tissue, the researchers examined the corneas of mice whose eyes had been infected with herpes simplex virus. They saw that cytotoxic T cells and T-helper cells — precursors for immune memory — had infiltrated the cornea and persisted for up to a month after the infection. Further investigations, including more intrusive microscopy techniques, revealed that the cytotoxic T cells had developed into long-lived memory cells that resided in the cornea.
The researchers then used live-cell imaging to observe the corneas of six healthy [human] adults. They found cells similar in shape, size and speed to the patrolling T cells in mice. ..."
From the abstract:
"The eye is considered immune privileged such that immune responses are dampened to protect vision. As the most anterior compartment of the eye, the cornea is exposed to pathogens and can mount immune responses that recruit effector T cells. However, presence of immune memory in the cornea is not defined. Here, we use intravital 2-photon microscopy to examine T cell responses in the cornea in mice. We show that recruitment of CD8+ T cells in response to ocular virus infection results in the formation of tissue-resident memory T (TRM) cells. Motile corneal TRM cells patrol the cornea and rapidly respond in situ to antigen rechallenge. ... In vivo imaging in humans also reveals highly motile cells that patrol the healthy cornea. Our study finds that TRM cells form in the cornea where they can provide local protective immunity."
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