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E. J. Lee, J. T. Rosenbaum, S. R. Planck; Newly Immigrant, but Not Resident, Dendritic Cells (DCs) in the Central Cornea Exhibit Mobility in Response to Pathologic Stimuli. Invest. Ophthalmol. Vis. Sci. 2007;48(13):183.
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Dendritic cells (DCs) are tissue sentinels that capture, process, and present antigens. DCs reside in the peripheral, and to a lesser extent, central cornea. We used in vivo microscopy to examine the dynamic response of central and peripheral DCs in murine cornea to various stimuli: injury, microbial product, inflammatory mediator, and live bacteria.
Mice expressing enhanced yellow fluorescent protein (eYFP) with the CD11c promoter (specific for DCs in mice) were used to visualize DCs in intact cornea or skin by fluorescence microscopy. To detect DC probing and migration, time-lapse videomicroscopy (1 frame/min for up to 120 min) was performed before and after stimulation. One of the following was applied to the central cornea of each eye (n=3/group): 1) silver nitrate burn, 2) LPS (intrastromal injection, 10 µg/1 µl), 3) recombinant TNFα (intrastromal injection, 1 ng/1 µl), or 4) P. aeruginosa (intrastromal injection, 500 cfu/1 µl). Control eyes (n=3/group except for burn) were injected with appropriate control media. In addition, some corneas were first injected intrastromally with microspheres to induce centripetal migration of DCs to the central cornea 5 d prior to inoculation with P. aeruginosa. For comparison, ear skin was also imaged in steady-state or after stimulation with recombinant TNFα (1 ng/1 µl s.c.). After video stabilization, individual cells were tracked by masked observers.
Within 6 h after stimulation, resident central corneal DCs (within central 1 mm of cornea) did not appear to migrate toward or away from the sites of burn, injected LPS or TNFα, or live bacteria. In contrast, lateral centripetal migration of DCs from peripheral and mid-peripheral cornea after TNFα stimulation was detectable (9.4±0.3 µm/h) beginning at ~12h. When bead-injected corneas were subsequently infected, DCs in the area of the injected bacteria exhibited enhanced retraction and extension of processes within 3 h infection. Also, DCs exhibited slight, but not significant, increased migration speed (10.0±0.6 µm/h) compared to before infection (9.7±0.2 µm/h). In the ear, after TNFα treatment, augmented probing and lateral migration of some DCs (8.5±0.3 µm/h) were noted, compared to steady-state where no migration was observed.
In vivo imaging indicates that resident central corneal DCs do not mobilize rapidly even to proximal threats and perturbations within the cornea. In contrast, once DCs have been provoked to migrate into the central cornea, they exhibit migratory capability and probing activity similar to stimulated DCs in the skin.
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