IMMUNOCYTOCHEMICAL STUDY OF RETINAL DIODE-LASER PHOTOCOAGULATION IN THE RAT

Aim - To determine the nature of the cellular infiltrate, alterations in cell adhesion molecules, and MHC II antigen expression in the rat r etina following diode laser retinal photocoagulation. Method - 20 norm al Lister rats underwent diode laser photocoagulation of the retina. F rozen sections ti om eyes enucleated at 0, 1, 5, 13, and 33 days post laser were examined for T cells (R7.3), CD4 T cells (W3/25), activated CD4 T cells (OX-40), CD8 T cells (OX-8), B cells (OX-33), and macroph ages (OX-42), MHC II antigen (OX-6), and E-Selectin-l, VCAM-1, and ICA M-1. Results - Retinal diode laser photocoagulation stimulated a wound healing response in the outer retina and choroid. The cellular infilt rate included macrophages and activated CD4 T cells at 13 and 33 days post laser. Glial cells in the inner plexiform and inner nuclear layer s expressed MHC II antigen at 24 hours only. ICAM-1 antigen was induce d in RPE cells and in Muller cells in the inner retina at all time int ervals post laser and intense staining for ICAM-1 was present around i ntraretinal migrated cells at 13 and 33 days post laser. VCAM-1 antige n expression was induced in the choroidal vascular endothelium and RPE at 13 and 33 days after laser as was E-Selectin-l antigen expression which was also evident focally at the external Limiting membrane in as sociation with migrated cells adjacent to the burn. Conclusions - Thes e results suggest that alterations in cell adhesion molecules may regu late the migration and activation of retinal pigment epithelium, macro phages and CD4 T cells at the outer blood-retinal barrier and choroid following diode laser photocoagulation of the normal Lister rat retina .