Purpose: To isolate dendritic cells (DC) from rat corneas and to examine their functions and surface markers in vitro.
Methods: Cells were isolated enzymatically from dissected rat corneas and cultured for various intervals of time. Dendritic cells were enriched immunomagnetically from corneal cell preparations using monoclonal antibodies against DC surface antigens and tested for functional activity in lymphocyte stimulation assays. In vivo migration of DC was induced by traumatizing the corneal epithelium. Wholemounts of epithelial sheets were stained immunofluorescently with anti-DC antibodies and examined by confocal microscopy. Dendritic cells isolated from traumatized corneas were tested for functional activity.
Results: Corneal DC exhibited the properties of other members of the DC family, i.e., low buoyant density, lymphoid DC-specific markers, and lymphostimulatory function. In fresh unfractionated cell preparations of normal cornea, no functional activity was detected. However, DC immunomagnetically purified from fresh preparations were functionally active. Injury to the corneal epithelium induced the migration of DC from the periphery to the central cornea; DC measured in this situation showed significantly increased functional activity. Finally, IL-1 beta and GM-CSF enhanced the functional activity of corneal DC.
Conclusions: Corneal DC have lymphostimulatory capacity in situ, but they may be maintained in a state of latency by the suppressive influence exerted by neighboring cells. Injury to the corneal epithelium results in functional activation of the corneal DC, which may be caused by cytokines such as IL-1 beta or GM-CSF. Thus, corneal DC may be important in the immune regulation of the anterior segment.