In Vivo Visualization of Intravascular Patrolling Immune Cells in the Primate Eye.

Area of Science:

• Ophthalmology
• Immunology
• Preclinical Research

Background:

• Understanding ocular immune status is crucial for treating eye diseases.
• Nonhuman primates (NHPs) are vital preclinical models in ophthalmology due to their similar visual and immune systems to humans.

Purpose of the Study:

• To demonstrate the utility of phase-contrast adaptive optics scanning light ophthalmoscopy (AOSLO) for visualizing cellular-scale immune cell dynamics in the NHP eye, label-free.
• To analyze immune cell behavior and morphology within the NHP retinal vasculature.

Main Methods:

• Phase-contrast AOSLO was employed to image retinal vasculature in five NHP eyes.
• Image analysis included motion correction, temporal averaging, and manual determination of cell counts, dimensions, velocities, and frequency.
• Immune cells were categorized by morphology: ovoid, semicircular, and flattened.

Main Results:

• Immune cells were observed migrating along vascular endothelium in both forward and reverse directions relative to blood flow.
• Cell velocity was consistent across different morphologies and vessel types (arterioles vs. venules).
• Venules exhibited a higher frequency of immune cells compared to arterioles, with a greater proportion of flattened cells observed in arterioles. These cells were identified as nonclassical patrolling monocytes (NCPMs).

Conclusions:

• Phase-contrast AOSLO enables label-free visualization of individual immune cell behaviors within the retinal circulation of NHPs.
• This technique offers a valuable tool for studying ocular immune responses without the confounding effects of contrast agents.