Abstract
Abstract: :
Purpose: Although there is ample evidence that antigen presentation takes place in the retina, details concerning the nature of the antigen presenting cells (APC) of the retina are unclear. We have isolated retina and enriched for the CD45+ cells to examine their in situ responsiveness to IFN-gamma and anti-CD40, which are known to upregulate activities associated with anitgen presentation. Methods: Mice were pretreated with systemic or intracameral inoculations of IFN-gamma or anti-CD40, or control inoculations. After 24 h, the retinas were harvested, enzymatically dissociated, positively selected with anti-CD45, and analyzed by flow cytometry using antibodies known to identify markers associated with APC. Results: Most of the CD45+ cells in the retina were CD11b+, F4/80+, CD8alpha+, CD80+, and MHC classIIlo, which is similar to CNS microglia (MG). There was also a small population of DEC-205+ cells, and a smaller number of CD11c+ cells. Both of these are markers of dendritic cells (DC). Intraocular inoculation of IFN-gamma led to a 2-fold increase in the number of CD45+ cells, and a modest upregulation of CD80 and MHC class II on CD11b+ cells. Intraocular inoculation of anti-CD40 also increased the total number of CD45+ cells, but increases in CD80 and I-A expression were minimal. The most signigicant change following anti-CD40 treatement was an increase in the number of CD11c+ cells, and increases in their expression of CD80 and CD11b Conclusions: No cells that could be conclusively identified as either perivascular cells (PVC) or DC were found, although two candidate populations were observed; the DEC-205+ cells, and the CD11c+ cells. The effects of IFN-gamma treatment were attenuated on cells in retina, relative to the local effect of IFN-gamma inoculation into a non-ocular tissue. Addition of IFN-gamma or anti-CD40 to cultures of CD45+ retinal cells also had relatively little effect on their expression levels of molecules known to be affected on APC from other tissues
Keywords: antigen presentation/processing • immune tolerance/privilege • immunomodulation/immunoregulation