Antigen presenting cells In the retina

Abstract

The presence and activity of dendritic cells (DC) in retina is controversial. This is in part due to the limited number of DC in the retina and the small number of reliable DC markers. In addition, functions ascribed to DC in other parts of the body are thought to be done by microglia in the central nervous system. CD11c is the cellular marker most associated with DC. In order to study the nature of retinal DC, transgenic mice that express green fluorescent protein (GFP) on the CD11c promoter were used to visualize, quantify, and characterize DC in both quiescent and injured retinas. In the quiescent retina it was found that compared to the number of neurons and microglial cells there were relatively few DC located in the nerve fiber layer and the outer plexiform layer. Upon retinal injury by either optic nerve crush or exposure to continuous bright light, the numbers of DC increased significantly and translocated to retinal layers associated with the injury. Surprisingly, the retinas of the eyes contralateral to the optic nerve crush also showed a significant increase in DC. The potential origin of the DC in retina was examined using a chimeric mouse paradigm. Most of the retinal DC were found to originate from circulating precursors, and a smaller number from a local progenitor cell population. This study suggests that retinal DC are a previously overlooked population, distinct from microglia, and may be important in the injury response and maintenance of homeostasis in the retina.